feat(api): ajoute un log service pour les logs de fonctionnement côté serveur

Jusqu'ici, rien ne journalisait quoi que ce soit côté serveur : aucune
trace au démarrage à part un console.log ad hoc, et surtout aucune trace
des requêtes ni des erreurs gérées par ErrorHandlerService — un 500 en
production n'aurait laissé aucune trace exploitable.

- LoggerService (apps/api/src/lib/logger.service.ts) — classe (public
  debug/info/warn/error, private emit), même convention que
  ErrorHandlerService (packages/error-tools) : instance unique partagée
  exportée (`export const logger = new LoggerService()`). Émet une ligne
  JSON structurée par appel (timestamp/level/message + meta), filtrée par
  seuil selon NODE_ENV (debug complet en dev, warn+ pendant les tests
  pour ne pas alourdir la sortie de Mocha, info+ en production). Seul
  endroit du code autorisé à toucher `console` directement (biome-ignore
  justifié), toujours via une méthode nommée — jamais un console.log nu.
- requestLogger (middlewares/request-logger.ts) — une ligne par requête
  terminée (méthode/chemin/statut/durée), montée en tout premier dans
  app.ts, avant même setupCore (CORS/JSON/cookies), pour englober tout le
  pipeline. Niveau déduit du statut (info/warn/error).
- errorLogger (middlewares/error-logger.ts) — monté juste avant
  createErrorMiddleware : réutilise errorHandlerService.handle() (pur/
  sans effet de bord) pour classifier l'erreur avant que la vraie réponse
  ne soit construite, log en warn les 4xx routiniers (validation, 404,
  401...) et en error les 5xx/exceptions non prévues (avec la stack).
- error-handler.service.ts : retire le `console.error(error)` ad hoc de
  fromUnknownError — errorLogger voit désormais chaque erreur avant que
  ce service ne la mappe, donc ce console.error faisait doublon (et
  loggait en texte brut, pas en JSON structuré).
- server.ts : le console.log de démarrage passe par logger.info.

Vérifié : pnpm --filter api test (303/303, dont 8 nouveaux tests sur
LoggerService), pnpm lint/build clean, testé en live (pnpm dev:api +
curl) — logs JSON corrects pour un 200, un 404, un 401.

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>

apps/api/src/app.ts

@@ -1,8 +1,10 @@
 import { errorHandlerService } from "@batch-cooking/error-tools";
-import { ExpressServer, createErrorMiddleware } from "@batch-cooking/express-tools";
+import { createErrorMiddleware, ExpressServer } from "@batch-cooking/express-tools";
 import { ErrorCode } from "@batch-cooking/shared";
 import type { Express, Request, Response } from "express";
 import { env } from "./config/env.js";
+import { errorLogger } from "./middlewares/error-logger.js";
+import { requestLogger } from "./middlewares/request-logger.js";
 import { authRouter } from "./modules/auth/auth.routes.js";
 import { houseRouter } from "./modules/house/house.routes.js";
 import { planningRouter } from "./modules/planning/planning.routes.js";
@@ -22,6 +24,12 @@ import { sourcesRouter } from "./modules/sources/sources.routes.js";
  */
 export function createServer(): ExpressServer {
   const server = new ExpressServer();
+  // First middleware registered, before even setupCore's own (CORS/JSON
+  // body parsing/cookies) — it only reads `req`/`res`, so it doesn't need
+  // to run after them, and mounting it first means it wraps the *whole*
+  // pipeline (its "finish" listener still fires for a request that never
+  // makes it past CORS/body-parsing, not just ones that reach a route).
+  server.addMiddleware(requestLogger);
   server.setupCore({ corsOrigin: env.CORS_ORIGIN });
 
   server.addRoute("get", "/health", (_req: Request, res: Response) => {
@@ -52,10 +60,12 @@ export function createServer(): ExpressServer {
     res.status(404).json({ code: ErrorCode.NOT_FOUND, message: "Not found" });
   });
 
-  // Final error-handling middleware: every thrown/`next(err)`-ed error in
-  // the app ends up here. All the "what status/body does this error map
-  // to" logic lives in ErrorHandlerService, from @batch-cooking/error-tools
-  // — this stays a thin adapter.
+  // Two error-handling middlewares in a row (Express runs them in
+  // registration order, same as regular middleware) — errorLogger logs the
+  // error, then hands it on (`next(err)`) to the real one: all the "what
+  // status/body does this error map to" logic lives in ErrorHandlerService,
+  // from @batch-cooking/error-tools — this stays a thin adapter.
+  server.setErrorHandler(errorLogger);
   server.setErrorHandler(createErrorMiddleware(errorHandlerService));
 
   return server;

apps/api/src/lib/logger.service.ts

@@ -0,0 +1,102 @@
+import { env } from "../config/env.js";
+
+/**
+ * Server-side operational logging — the one place in this codebase allowed
+ * to call `console.*` directly (see `biome.json`'s `noConsole`, which bans
+ * bare `console.log` everywhere else: every log line here goes through a
+ * named level instead, `logger.info(...)`/`logger.error(...)`, never an
+ * unlabeled dump of text). Everything else (the request logger, `server.ts`'s
+ * startup line, the error middleware) goes through this instead of touching
+ * `console` itself, so there's exactly one place that decides the log
+ * *shape* (structured JSON lines — one object per line, trivially
+ * grep/parse-able by `docker logs`/Portainer or any log aggregator, unlike
+ * free-form `console.log` text).
+ *
+ * A class, not a plain object literal — same convention as
+ * `ErrorHandlerService` (`packages/error-tools`): `public` methods are the
+ * actual API, `private` ones are internals a caller never touches directly.
+ * `export const logger = new LoggerService()` below is the single shared
+ * instance every caller imports — there's exactly one log stream for the
+ * whole process, nothing to parameterize per call site, so nobody
+ * constructs their own.
+ */
+
+/** Ascending severity — mirrors the standard `debug < info < warn < error` convention. */
+export type LogLevel = "debug" | "info" | "warn" | "error";
+
+/** Arbitrary structured context attached to a log line (a request id, a duration, an error's own fields, …) — merged into the emitted JSON object, never interpolated into the message string itself. */
+export type LogMeta = Record<string, unknown>;
+
+const LEVEL_SEVERITY: Record<LogLevel, number> = {
+  debug: 0,
+  info: 1,
+  warn: 2,
+  error: 3,
+};
+
+/**
+ * Lines below this level are dropped rather than emitted — keeps `debug`
+ * out of production (verbose, meant for local troubleshooting only) and
+ * out of the test suite's own output (Mocha's reporter is noisy enough
+ * already), while `pnpm dev:api` sees everything. A free function, not a
+ * method — exported (unlike the rest of this module's internals) purely so
+ * `logger.service.test.ts` can exercise the three `NODE_ENV` cases
+ * directly, without needing a `LoggerService` instance at all.
+ */
+export function minLevelFor(nodeEnv: typeof env.NODE_ENV): LogLevel {
+  if (nodeEnv === "production") return "info";
+  if (nodeEnv === "test") return "warn";
+  return "debug";
+}
+
+/** Console method each level writes through — `error`/`warn` go to stderr (their own native behavior), `debug`/`info` to stdout, the usual split log aggregators expect. */
+const CONSOLE_METHOD: Record<LogLevel, "debug" | "info" | "warn" | "error"> = {
+  debug: "debug",
+  info: "info",
+  warn: "warn",
+  error: "error",
+};
+
+/** Server-side operational logger — see the module doc comment for why this exists and what it's for. */
+export class LoggerService {
+  /** Computed once at construction from `env.NODE_ENV` — see {@link minLevelFor}. */
+  private readonly minSeverity: number;
+
+  public constructor(nodeEnv: typeof env.NODE_ENV = env.NODE_ENV) {
+    this.minSeverity = LEVEL_SEVERITY[minLevelFor(nodeEnv)];
+  }
+
+  public debug(message: string, meta?: LogMeta): void {
+    this.emit("debug", message, meta);
+  }
+
+  public info(message: string, meta?: LogMeta): void {
+    this.emit("info", message, meta);
+  }
+
+  public warn(message: string, meta?: LogMeta): void {
+    this.emit("warn", message, meta);
+  }
+
+  public error(message: string, meta?: LogMeta): void {
+    this.emit("error", message, meta);
+  }
+
+  private emit(level: LogLevel, message: string, meta?: LogMeta): void {
+    if (LEVEL_SEVERITY[level] < this.minSeverity) return;
+
+    // `meta` spread first so a caller accidentally passing e.g. `{ message:
+    // ... }` in it can never shadow the line's own core fields.
+    const line = {
+      ...meta,
+      timestamp: new Date().toISOString(),
+      level,
+      message,
+    };
+    // biome-ignore lint/suspicious/noConsole: this is the one place allowed to — see the class doc comment above.
+    console[CONSOLE_METHOD[level]](JSON.stringify(line));
+  }
+}
+
+/** Single shared instance — this service has no per-call-site state to isolate, same reasoning as `errorHandlerService`. */
+export const logger = new LoggerService();

apps/api/src/middlewares/error-logger.ts

@@ -0,0 +1,40 @@
+import { errorHandlerService } from "@batch-cooking/error-tools";
+import type { NextFunction, Request, Response } from "express";
+import { logger } from "../lib/logger.service.js";
+
+/**
+ * Logs every error that reaches Express's error-handling chain, then
+ * passes it straight on (`next(err)`) to the real error-to-response
+ * middleware (`createErrorMiddleware`, `@batch-cooking/express-tools`) —
+ * mounted immediately after this one in `app.ts`. Reuses
+ * `errorHandlerService.handle()` (`@batch-cooking/error-tools`) just to
+ * classify the error for logging purposes (its `status`/`body.code`) —
+ * `.handle()` is pure/stateless, so calling it here and then again in
+ * `createErrorMiddleware` right after is harmless, and it's the one place
+ * that already knows a bare `ZodError` maps to `400 VALIDATION_ERROR`, an
+ * `HttpError` maps to its own `status`/`code`, and anything else is a
+ * `500`. Doesn't build the actual response itself — that's still
+ * `createErrorMiddleware`'s job.
+ *
+ * A resulting `4xx` is routine, expected operation (a validation failure,
+ * a 404, an unauthenticated request) — logged at `warn`, not `error`, so a
+ * genuine `5xx` (an unhandled exception, a bug) stands out instead of
+ * being buried under normal client mistakes.
+ */
+export function errorLogger(err: unknown, req: Request, _res: Response, next: NextFunction): void {
+  const meta = { method: req.method, path: req.originalUrl };
+  const { status, body } = errorHandlerService.handle(err);
+
+  if (status >= 500) {
+    logger.error(err instanceof Error ? err.message : body.message, {
+      ...meta,
+      status,
+      code: body.code,
+      stack: err instanceof Error ? err.stack : undefined,
+    });
+  } else {
+    logger.warn(body.message, { ...meta, status, code: body.code });
+  }
+
+  next(err);
+}

apps/api/src/middlewares/request-logger.ts

@@ -0,0 +1,45 @@
+import type { NextFunction, Request, Response } from "express";
+import { logger } from "../lib/logger.service.js";
+
+/**
+ * Logs one line per request once it finishes — method, path, status code,
+ * and duration. Mounted first in `app.ts` (before every route, and before
+ * the error handler) so it wraps the whole request/response cycle,
+ * including requests that end in a 404 or an error response.
+ *
+ * Listens on `res`'s `"finish"` event rather than wrapping `next()` in a
+ * `try`/`finally`: this middleware calls `next()` immediately and returns,
+ * so it never itself sits on the stack waiting for the rest of the
+ * pipeline to resolve — `"finish"` fires once Express has actually flushed
+ * the response, whichever handler (or the error middleware) produced it.
+ *
+ * `4xx`/`5xx` responses log at `warn`/`error` respectively (status alone
+ * decides the level — this middleware has no idea *why* a request failed,
+ * just that it did); everything else logs at `info`. A route's own
+ * handler/the error middleware may log more detail about *why* separately
+ * (see `error-middleware` wiring in `app.ts`) — this line is just the
+ * "a request happened, here's the outcome" operational trace.
+ */
+export function requestLogger(req: Request, res: Response, next: NextFunction): void {
+  const startedAt = process.hrtime.bigint();
+
+  res.on("finish", () => {
+    const durationMs = Number(process.hrtime.bigint() - startedAt) / 1_000_000;
+    const meta = {
+      method: req.method,
+      path: req.originalUrl,
+      status: res.statusCode,
+      durationMs: Math.round(durationMs * 100) / 100,
+    };
+
+    if (res.statusCode >= 500) {
+      logger.error("Request completed", meta);
+    } else if (res.statusCode >= 400) {
+      logger.warn("Request completed", meta);
+    } else {
+      logger.info("Request completed", meta);
+    }
+  });
+
+  next();
+}

apps/api/src/server.ts

@@ -1,5 +1,6 @@
 import { createServer } from "./app.js";
 import { env } from "./config/env.js";
+import { logger } from "./lib/logger.service.js";
 import { registerAllRecipeSources } from "./sources/index.js";
 
 // Populates the recipe-source registry (recipe-source-registry.ts) before
@@ -10,5 +11,5 @@ registerAllRecipeSources();
 const server = createServer();
 
 server.listen(env.PORT, () => {
-  console.log(`API listening on http://localhost:${env.PORT}`);
+  logger.info("API listening", { port: env.PORT, nodeEnv: env.NODE_ENV });
 });

apps/api/test/logger.service.test.ts

@@ -0,0 +1,105 @@
+import { expect } from "chai";
+import { LoggerService, logger, minLevelFor } from "../src/lib/logger.service.js";
+
+/**
+ * Stubs one `console` method for one test, capturing every call instead of
+ * actually writing to stdout/stderr — same "stub the one thing that
+ * touches the outside world" approach `the-meal-db.test.ts` uses for
+ * `fetch`. Restored by the caller (`afterEach` below) regardless of which
+ * test used it.
+ */
+function stubConsoleMethod(method: "debug" | "info" | "warn" | "error") {
+  const calls: unknown[][] = [];
+  // biome-ignore lint/suspicious/noConsole: this *is* the console-stubbing helper — it has to read the real method to be able to restore it. Never calls it for real.
+  const original = console[method];
+  console[method] = (...args: unknown[]) => {
+    calls.push(args);
+  };
+  return {
+    calls,
+    restore: () => (console[method] = original),
+  };
+}
+
+describe("logger.service", () => {
+  describe("minLevelFor", () => {
+    it("only lets warn/error through in test — Mocha's own output shouldn't get any noisier", () => {
+      expect(minLevelFor("test")).to.equal("warn");
+    });
+
+    it("only lets info/warn/error through in production — debug is too verbose to ship", () => {
+      expect(minLevelFor("production")).to.equal("info");
+    });
+
+    it("lets everything through, including debug, in development", () => {
+      expect(minLevelFor("development")).to.equal("debug");
+    });
+  });
+
+  describe("logger", () => {
+    let stub: ReturnType<typeof stubConsoleMethod>;
+
+    afterEach(() => {
+      stub?.restore();
+    });
+
+    it("emits a warn line as a single JSON object via console.warn, with a timestamp/level/message and any extra meta merged in", () => {
+      stub = stubConsoleMethod("warn");
+
+      logger.warn("Something routine failed", { status: 404, code: 4049 });
+
+      expect(stub.calls).to.have.length(1);
+      const [line] = stub.calls[0];
+      const parsed = JSON.parse(line as string);
+      expect(parsed.level).to.equal("warn");
+      expect(parsed.message).to.equal("Something routine failed");
+      expect(parsed.status).to.equal(404);
+      expect(parsed.code).to.equal(4049);
+      expect(new Date(parsed.timestamp).toString()).to.not.equal("Invalid Date");
+    });
+
+    it("emits an error line via console.error", () => {
+      stub = stubConsoleMethod("error");
+
+      logger.error("Something broke");
+
+      expect(stub.calls).to.have.length(1);
+      const parsed = JSON.parse(stub.calls[0][0] as string);
+      expect(parsed.level).to.equal("error");
+    });
+
+    it('drops debug/info under the test suite\'s own NODE_ENV=test (minLevelFor("test") === "warn")', () => {
+      const debugStub = stubConsoleMethod("debug");
+      const infoStub = stubConsoleMethod("info");
+
+      logger.debug("Should not appear");
+      logger.info("Should not appear either");
+
+      expect(debugStub.calls).to.have.length(0);
+      expect(infoStub.calls).to.have.length(0);
+      debugStub.restore();
+      infoStub.restore();
+    });
+
+    it("never lets meta override the line's own timestamp/level/message keys", () => {
+      stub = stubConsoleMethod("warn");
+
+      logger.warn("Real message", { message: "spoofed", level: "spoofed", timestamp: "spoofed" });
+
+      const parsed = JSON.parse(stub.calls[0][0] as string);
+      expect(parsed.message).to.equal("Real message");
+      expect(parsed.level).to.equal("warn");
+      expect(new Date(parsed.timestamp).toString()).to.not.equal("Invalid Date");
+    });
+
+    it('a separate instance constructed with nodeEnv="development" lets debug through, independently of the shared logger\'s own NODE_ENV=test threshold', () => {
+      const debugStub = stubConsoleMethod("debug");
+      const devLogger = new LoggerService("development");
+
+      devLogger.debug("Visible in dev");
+
+      expect(debugStub.calls).to.have.length(1);
+      debugStub.restore();
+    });
+  });
+});

packages/error-tools/src/error-handler.service.ts

@@ -60,11 +60,15 @@ export class ErrorHandlerService {
   }
 
   /**
-   * Anything unrecognized: logged server-side (so it's still diagnosable)
-   * but never leaks internal details to the client — always a generic 500.
+   * Anything unrecognized: never leaks internal details to the client —
+   * always a generic 500. Doesn't log the error itself — this class only
+   * maps an error to `{ status, body }` (see the class doc comment); a
+   * caller wanting this logged server-side does so on its own before/
+   * around calling `handle()` (see `apps/api`'s `errorLogger` middleware,
+   * which sees every error — including this exact "unrecognized" case —
+   * before it ever reaches here).
    */
-  private fromUnknownError(error: unknown): ErrorHandlingResult {
-    console.error(error);
+  private fromUnknownError(_error: unknown): ErrorHandlingResult {
     return {
       status: 500,
       body: { code: ErrorCode.INTERNAL_ERROR, message: "Internal server error" },