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/mail.php

@@ -11,6 +11,11 @@ $user = require_auth();
 $userId = (int)$user['id'];
 $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'] ?? '');
@@ -20,8 +25,9 @@ try {
     if ($action === 'get_inbox') {
         $limit = isset($_GET['limit']) ? (int)$_GET['limit'] : 25;
         $unreadOnly = !empty($_GET['unread_only']) && $_GET['unread_only'] === '1';
+        $forceRefresh = !empty($_GET['refresh']) && $_GET['refresh'] === '1';
 
-        $res = microsoft_fetch_inbox_messages($userId, $limit, $unreadOnly);
+        $res = microsoft_fetch_inbox_messages($userId, $limit, $unreadOnly, $forceRefresh);
         echo json_encode($res);
         exit;
     }