fix: Sign out + login flow + cache bust for i18n

- auth.js: window.handleLogout at module top level (was inside
  renderUserMenu, not always called). Fixes settings dropdown
  'Sign out' onclick='handleLogout()' doing nothing.
- auth.js: add missing imports (loadVaults, loadTags from sidebar.js)
  and dynamic import for IndexUpdateManager (circular dep avoidance).
  Fixes 'loadVaults is not defined' error on login.
- sw.js: CACHE_VERSION v4→v5 to bust stale Service Worker cache
  that was serving old viewer.js without data-i18n attributes,
  causing dashboard tabs to stay French despite English profile.

To apply: rebuild container + unregister SW in DevTools + reload.

frontend/js/auth.js

@@ -4,6 +4,15 @@ import { safeCreateIcons } from './utils.js';
 import { showToast, closeHeaderMenu } from './ui.js';
 import { t, getLocale } from './i18n.js';
 import { showWelcome } from './viewer.js';
+import { loadVaults, loadTags } from './sidebar.js';
+
+// ── Global logout handler for header dropdown onclick ────────────────────
+// Defined at module top level so it's always available, even if
+// renderUserMenu() hasn't been called yet.
+// Uses a getter to lazy-resolve AuthManager (defined later in this module).
+window.handleLogout = () => {
+  AuthManager.logout();
+};
 
 // ---------------------------------------------------------------------------
 // API helpers
@@ -201,9 +210,6 @@ const AuthManager = {
     const logoutBtn = document.getElementById("logout-btn");
     if (logoutBtn) logoutBtn.addEventListener("click", () => AuthManager.logout());
 
-    // Also wire up the header dropdown "Sign out" (onclick="handleLogout()")
-    window.handleLogout = () => AuthManager.logout();
-
     const adminRow = document.getElementById("admin-menu-row");
     if (adminRow) {
       if (user.role === "admin") {
@@ -313,7 +319,8 @@ function initLoginForm() {
       // Load app data after successful login
       try {
         await Promise.all([loadVaults(), loadTags()]);
-        // Start SSE sync now that auth cookie is set
+        // Start SSE sync now that auth cookie is set (dynamic import to avoid circular dep)
+        const { IndexUpdateManager } = await import('./sync.js');
         IndexUpdateManager.connect();
         // Show dashboard
         showWelcome();

frontend/sw.js

@@ -1,6 +1,6 @@
 /* ObsiGate Service Worker - PWA v2 with IndexedDB offline support */
 
-const CACHE_VERSION = 'obsigate-v4-pwa';
+const CACHE_VERSION = 'obsigate-v5-pwa';
 const STATIC_CACHE = CACHE_VERSION + '-static';
 const DYNAMIC_CACHE = CACHE_VERSION + '-dynamic';
 const MAX_DYNAMIC_CACHE_SIZE = 100;