Replace hardcoded French strings with i18n calls

Initialize i18n before auth so t() works when rendering
auth-dependent UI, and build the command palette lazily so
translations are loaded first. Bump service worker cache version.

frontend/js/app.js

@@ -23,12 +23,14 @@ import { initMermaid, setupFocusMode } from './mermaid-viewer.js';
 // Initialization — mirrors the original app.js init() ordering
 // =========================================================================
 async function init() {
-  // 1. Init auth first — needed for server-side language preference
-  const authOk = await Auth.AuthManager.initAuth();
-
-  // 2. Init i18n after auth so server language preference is available
+  // 1. Init i18n FIRST — loads fallback (FR) + selected locale
+  //    Server language check may fail (no auth yet), falls to localStorage
+  //    LocalStorage has correct language if user set it previously
   await initI18n();
 
+  // 2. Init auth — now t() works inside showApp()/renderUserMenu()
+  const authOk = await Auth.AuthManager.initAuth();
+
   UI.initTheme();
   UI.initHeaderMenu();
   UI.initCustomDropdowns();