feat(web): passe responsive téléphone pour le contenu des pages (#39 phase 3)

Réutilise la philosophie déjà en place pour la sidebar (défilement
horizontal plutôt que compression illisible) au lieu d'un nouveau patron
par page. Tout est strictement additif sous 640px — le rendu desktop est
inchangé.

- `AppLayout.scss` : `.app-content` passe de `--space-xl` (32px) à
  `--space-md` (16px) sous 640px — 64px de largeur utile récupérés sur un
  écran de ~375px.
- `planning-page.scss` : la grille 7 jours défile déjà horizontalement
  (`overflow: auto` + `min-width: 62rem`) ; ce qui casse au tactile, c'est
  le `✕` de suppression d'une recette (`opacity: 0` hors survol) — épinglé
  visible + cible tactile agrandie sous 640px, idem le bouton « + ».
- `dialog.scss` : `.dialog-panel` garde une gouttière latérale et gagne en
  hauteur utile sous 640px (le `--space-2xl` vertical est trop cher sur un
  écran court).
- `recipe-picker-dialog.scss` : le split 2 colonnes forcé du catalogue
  (plus spécifique que le `@media` de recipes.scss) repasse à une colonne
  sous 640px.

Tests : `layout.cy.ts` gagne un bloc « page content under 640px » —
padding de `.app-content`, grille sur son propre scroll sans déborder la
page, `✕` visible au tactile. 10/10 en local.

Refs #39
Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>

apps/web/cypress/e2e/layout.cy.ts

@@ -213,6 +213,84 @@ describe("Responsive breakpoint — sidebar becomes a horizontal top bar under 6
   });
 });
 
+describe("Responsive breakpoint — page content under 640px (issue #39)", () => {
+  const PHONE: [number, number] = [375, 812];
+
+  beforeEach(() => {
+    interceptAuth();
+  });
+
+  it("tightens .app-content padding from 32px to 16px on a phone", () => {
+    cy.intercept("GET", /\/planning\?/, { statusCode: 200, body: null });
+
+    cy.viewport(1600, 900);
+    cy.visit("/");
+    cy.get(".app-content").should(($el) => {
+      const s = getComputedStyle($el[0]);
+      // Desktop: var(--space-xl) === 2rem === 32px, all four sides.
+      expect(s.paddingTop).to.equal("32px");
+      expect(s.paddingLeft).to.equal("32px");
+    });
+
+    cy.viewport(...PHONE);
+    cy.visit("/");
+    cy.get(".app-content").should(($el) => {
+      const s = getComputedStyle($el[0]);
+      // Phone: var(--space-md) === 1rem === 16px.
+      expect(s.paddingTop).to.equal("16px");
+      expect(s.paddingLeft).to.equal("16px");
+    });
+  });
+
+  it("keeps the 7-day planning grid on its own horizontal scroll rather than overflowing the page", () => {
+    cy.intercept("GET", /\/planning\?/, {
+      statusCode: 200,
+      body: {
+        id: 1,
+        startDate: "2026-08-17T00:00:00.000Z",
+        finishDate: "2026-08-23T00:00:00.000Z",
+        items: [
+          {
+            id: 1,
+            weekDay: "lundi",
+            meal: "dejeuner",
+            portions: 4,
+            portionsRequested: 4,
+            discardedPortions: 0,
+            sourceItem: null,
+            recipe: { id: 1, name: "Curry de lentilles" },
+          },
+        ],
+      },
+    });
+
+    cy.viewport(...PHONE);
+    cy.visit("/");
+
+    // The grid wrapper is the scroll container, and its content is genuinely
+    // wider than the phone viewport (7 columns never crushed).
+    cy.get(".planning-grid-wrapper").should(($el) => {
+      expect(getComputedStyle($el[0]).overflowX).to.be.oneOf(["auto", "scroll"]);
+      expect($el[0].scrollWidth).to.be.greaterThan($el[0].clientWidth);
+    });
+
+    // ...and that overflow stays *inside* the wrapper — the document itself
+    // never scrolls sideways (global rule against a horizontally-scrolling
+    // body).
+    cy.document()
+      .its("documentElement.scrollWidth")
+      .should("be.lte", 375 + 1);
+
+    // The per-recipe remove "✕" is hover-gated on desktop; on touch it must
+    // be permanently visible or a planned recipe can't be removed at all.
+    cy.get(".recipe-chip__remove")
+      .first()
+      .should(($btn) => {
+        expect(Number(getComputedStyle($btn[0]).opacity)).to.be.greaterThan(0);
+      });
+  });
+});
+
 describe("Color theme — light/dark tokens actually reach the rendered chrome", () => {
   beforeEach(() => {
     interceptAuth();

apps/web/src/components/ui/dialog.scss

@@ -23,6 +23,16 @@
   &::backdrop {
     background: rgba(0, 0, 0, 0.45);
   }
+
+  // On a phone the `48rem` cap is irrelevant (the viewport is narrower),
+  // but the `var(--space-2xl)` top/bottom breathing room is a large slice
+  // of a short screen — tighten it so a form-heavy dialog isn't
+  // needlessly cramped, and keep a small side gutter so the panel never
+  // sits edge to edge.
+  @media (max-width: 640px) {
+    max-width: calc(100vw - var(--space-md));
+    max-height: calc(100vh - var(--space-md));
+  }
 }
 
 .dialog-panel__header {

apps/web/src/features/planning/recipe-picker-dialog.scss

@@ -55,6 +55,17 @@
   .recipes-page__catalog {
     grid-template-columns: minmax(0, 3fr) minmax(0, 2fr);
   }
+
+  // recipes.scss already collapses `&__catalog` to a single column under
+  // 1024px, but the rule just above (2 classes) outweighs that page-scoped
+  // `@media` block and would keep two ~90px columns side by side on a
+  // phone. Re-collapse it here for the dialog's own narrow case — the list
+  // then stacks above the detail pane, same as the full `/recettes` page.
+  @media (max-width: 640px) {
+    .recipes-page__catalog {
+      grid-template-columns: 1fr;
+    }
+  }
 }
 
 .recipe-picker__filters {

apps/web/src/layouts/AppLayout.scss

@@ -365,6 +365,15 @@
     flex-direction: column;
   }
 
+  // The desktop `var(--space-xl)` (32px) all around eats a big share of a
+  // ~375px screen — every page then has ~64px less usable width than the
+  // viewport already gives it. Drop to `--space-md` (16px) on phones; the
+  // grid/table pages that still overflow fall back to their own horizontal
+  // scroll (same philosophy as the sidebar below).
+  .app-content {
+    padding: var(--space-md);
+  }
+
   .app-sidebar {
     flex-direction: row;
     align-items: center;

apps/web/src/pages/planning/planning-page.scss

@@ -264,3 +264,29 @@ table.planning-grid {
     background: color-mix(in srgb, var(--color-primary) 8%, transparent);
   }
 }
+
+// --- Phone (issue #39, responsive pass) -----------------------------------
+// The grid itself already degrades gracefully on a narrow screen — the
+// wrapper's `overflow: auto` + the table's `min-width: 62rem` mean it just
+// scrolls horizontally rather than crushing seven day-columns into
+// illegibility (same philosophy as the sidebar's own fallback). What does
+// NOT survive the switch to touch are the two hover-gated affordances
+// below.
+@media (max-width: 640px) {
+  // `.recipe-chip__remove` sits at `opacity: 0` until its chip is hovered
+  // — invisible, and untappable, on a touch screen where nothing is ever
+  // "hovered". Pin it visible so a planned recipe can actually be removed
+  // on a phone. Also give it a real tap target.
+  .recipe-chip__remove {
+    opacity: 0.7;
+    width: 1.5rem;
+    height: 1.5rem;
+    font-size: 0.8rem;
+  }
+
+  // A slightly taller "+" so adding to a slot is a comfortable tap, not a
+  // 5px sliver.
+  .add-recipe-btn {
+    padding: var(--space-sm);
+  }
+}