fix: refactor logout to use synchronous flow with full page redirect

- Rewrite logout() from async to synchronous to prevent React re-renders with stale state
- Replace router.push('/login') with redirectToLogin() (window.location.replace) in all page auth guards for reliable navigation in Edge/Safari
- Add performFullLogout() helper that clears auth state, feature stores, and localStorage
- Fix persist middleware partialize to return {} when not authenticated, preventing state resurrection
- Use keepalive fetch for background cookie/token cleanup so redirect fires immediately
- Remove unused useRouter imports from page.tsx and contacts/page.tsx
- Simplify all page logout handlers to directly call logout()

Fixes #63

app/[locale]/calendar/page.tsx

@@ -11,7 +11,7 @@ import {
 } from "date-fns";
 import { useCalendarStore } from "@/stores/calendar-store";
 import { isCalendarViewMode } from "@/stores/calendar-store";
-import { useAuthStore } from "@/stores/auth-store";
+import { useAuthStore, redirectToLogin } from "@/stores/auth-store";
 import { useEmailStore } from "@/stores/email-store";
 import { useSettingsStore } from "@/stores/settings-store";
 import { useIdentityStore } from "@/stores/identity-store";
@@ -105,7 +105,7 @@ export default function CalendarPage() {
   useEffect(() => {
     if (initialCheckDone && !isAuthenticated && !authLoading) {
       try { sessionStorage.setItem('redirect_after_login', window.location.pathname); } catch { /* ignore */ }
-      router.push("/login");
+      redirectToLogin();
     } else if (client && !supportsCalendar) {
       router.push("/");
     }
@@ -721,7 +721,7 @@ export default function CalendarPage() {
             collapsed
             quota={quota}
             isPushConnected={isPushConnected}
-            onLogout={() => { logout(); if (!useAuthStore.getState().isAuthenticated) router.push('/login'); }}
+            onLogout={logout}
             onManageApps={handleManageApps}
             onInlineApp={handleInlineApp}
             onCloseInlineApp={closeInlineApp}