fix(mobile): lance la vérification de mise à jour à chaque ouverture (#106)

`useAppUpdateCheck` tournait au montage de `<UpdateBanner />`, mais celui-ci
n'était monté que dans `AppLayout`, derrière `RequireAuth` : un utilisateur
non connecté sur l'app native voit `LandingPage`, `AppLayout` n'est jamais
monté, donc aucune vérification tant qu'on n'est pas connecté — alors que
le back suppose l'inverse (`mobile.routes.ts` : « runs on every app start,
session or not »).

- `<UpdateBanner />` monté dans `App.tsx`, hors `<Routes>`, donc rendu pour
  toute route quel que soit l'état d'auth. Garde `!isNativePlatform()` et
  throttle 6 h inchangés ; rend toujours `null` sur le web.
- `update-banner.scss` : passe en `position: fixed` (bandeau haut,
  `env(safe-area-inset-top)`, `z-index: 100`) pour ne pas entrer dans la
  mise en page / le calcul de hauteur d'une page routée (`.app-layout` est
  `height: 100vh; overflow: hidden`).

Pas de test e2e : `Capacitor.isNativePlatform()` n'a pas de couture pour
simuler le natif depuis un run web (posture déjà assumée pour
`useAppUpdateCheck` / `UpdateBanner`, voir `app-settings-page.cy.ts`). Suite
e2e existante (layout / smoke / app-settings) revérifiée : aucun régression.

Closes #106

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

apps/web/src/App.tsx

@@ -1,6 +1,7 @@
 import { Navigate, Outlet, Route, Routes } from "react-router-dom";
 import { AdminAuthProvider } from "./features/admin/AdminAuthContext";
 import { RequireAdmin } from "./features/admin/RequireAdmin";
+import { UpdateBanner } from "./features/app-update/UpdateBanner";
 import { RedirectIfAuthenticated } from "./features/auth/RedirectIfAuthenticated";
 import { RequireAuth } from "./features/auth/RequireAuth";
 import { AdminLayout } from "./layouts/AdminLayout";
@@ -71,9 +72,17 @@ import { ShoppingListPage } from "./pages/shopping-list/ShoppingListPage";
  * never nested under `RequireAuth`. `/admin/login` is the only
  * unauthenticated admin route; everything else sits under `RequireAdmin` +
  * `AdminLayout`.
+ *
+ * {@link UpdateBanner} is mounted here, outside `<Routes>`, rather than in
+ * `AppLayout` — the native app-update check (issue #66) must run on every
+ * app start, session or not, and `AppLayout` only mounts once a visitor is
+ * past `RequireAuth`. It's a `position: fixed` strip and renders nothing on
+ * the web, so mounting it app-wide costs the routed pages no layout.
  */
 export function App() {
   return (
+    <>
+      <UpdateBanner />
       <Routes>
         <Route
           element={
@@ -177,5 +186,6 @@ export function App() {
         </Route>
         <Route path="*" element={<Navigate to="/" replace />} />
       </Routes>
+    </>
   );
 }

apps/web/src/features/app-update/update-banner.scss

@@ -1,18 +1,28 @@
-// Styles for UpdateBanner — a discreet, dismissible strip above the routed
-// page content (see AppLayout.tsx). Uses --color-warning the same way
-// source-item-preview__hint does elsewhere in the app: "worth noticing",
+// Styles for UpdateBanner — a discreet, dismissible strip pinned to the top
+// of the screen. Mounted app-wide in App.tsx (outside `<Routes>`) so the
+// native update check runs session or not, hence `position: fixed` rather
+// than the old in-flow placement inside `.app-content`: this way it never
+// enters any routed page's layout / height math (`.app-layout` is
+// `height: 100vh; overflow: hidden`), it just overlays. Native-only —
+// renders nothing on the web (see UpdateBanner.tsx). Uses --color-warning
+// the same way source-item-preview__hint does elsewhere: "worth noticing",
 // not an error.
 .update-banner {
+  position: fixed;
+  top: 0;
+  left: 0;
+  right: 0;
+  z-index: 100;
   display: flex;
   flex-wrap: wrap;
   align-items: center;
   justify-content: space-between;
   gap: var(--space-sm);
-  margin-bottom: var(--space-md);
   padding: var(--space-sm) var(--space-md);
+  // Clears the Android status bar when the WebView draws under it.
+  padding-top: calc(var(--space-sm) + env(safe-area-inset-top, 0px));
   background: color-mix(in srgb, var(--color-warning) 12%, var(--color-surface));
-  border: 1px solid var(--color-warning);
-  border-radius: var(--radius-base);
+  border-bottom: 1px solid var(--color-warning);
   font-size: var(--font-size-sm);
 
   &__text {

apps/web/src/layouts/AppLayout.tsx

@@ -2,7 +2,6 @@ import { useState } from "react";
 import { useTranslation } from "react-i18next";
 import { NavLink, Outlet, useLocation, useNavigate } from "react-router-dom";
 import { BottomSheet } from "../components/ui/BottomSheet";
-import { UpdateBanner } from "../features/app-update/UpdateBanner";
 import { useAuth } from "../features/auth/AuthContext";
 import { useIsMobileViewport } from "../lib/useIsMobileViewport";
 import "./AppLayout.scss";
@@ -148,9 +147,9 @@ export function AppLayout() {
       )}
 
       <main className={isMobile ? "app-content app-content--with-bottom-nav" : "app-content"}>
-        {/* Renders nothing on the web build (native-only check) or once no
-            newer version is known — see UpdateBanner's own doc comment. */}
-        <UpdateBanner />
+        {/* `UpdateBanner` used to sit here, but the native update check
+            (issue #66) must run session or not — it's mounted app-wide in
+            `App.tsx` now, as a `position: fixed` strip. */}
         <Outlet />
       </main>