feat(cache): implement centralized caching layer for improved performance and reduced API calls

feat(microsoft-integration): enhance inbox and events fetching with caching support
feat(auth): include theme and notification settings in user data retrieval
feat(profile): improve password visibility toggle functionality
feat(planner): optimize event synchronization with Outlook using caching
fix(notifications): update mail badge handling for mobile and desktop

api/notifications.php

@@ -9,6 +9,11 @@ require_once __DIR__ . '/../includes/integrations/microsoft.php';
 $user = require_auth();
 $db = get_db_connection();
 
+// Geef het PHP sessieslot direct vrij zodat paginanavigatie nooit geblokkeerd wordt
+if (session_status() === PHP_SESSION_ACTIVE) {
+    session_write_close();
+}
+
 header('Content-Type: application/json; charset=utf-8');
 
 $action = $_GET['action'] ?? ($_POST['action'] ?? '');