feat: add automatic identity synchronization (#167)

hooks/use-identity-sync.ts

@@ -0,0 +1,31 @@
+'use client';
+
+import { useEffect } from 'react';
+import { useAuthStore } from '@/stores/auth-store';
+
+// Re-sync identities every 30 minutes while the app is open
+const SYNC_INTERVAL_MS = 30 * 60 * 1000;
+
+export function useIdentitySync() {
+  const isAuthenticated = useAuthStore((s) => s.isAuthenticated);
+  const refreshIdentities = useAuthStore((s) => s.refreshIdentities);
+
+  useEffect(() => {
+    if (!isAuthenticated) return;
+
+    // Sync when the user returns to the tab (e.g. after adding an alias in Stalwart)
+    const handleVisibilityChange = () => {
+      if (document.visibilityState === 'visible') {
+        refreshIdentities();
+      }
+    };
+
+    document.addEventListener('visibilitychange', handleVisibilityChange);
+    const interval = setInterval(refreshIdentities, SYNC_INTERVAL_MS);
+
+    return () => {
+      document.removeEventListener('visibilitychange', handleVisibilityChange);
+      clearInterval(interval);
+    };
+  }, [isAuthenticated, refreshIdentities]);
+}