feat(calendar): add reminder functionality for events with notifications

src/contexts/NotificationContext.jsx

@@ -77,6 +77,15 @@ export function NotificationProvider({ children }) {
         seenIds.current.add(n.id);
         const icon = notificationIcon(n.type);
         toast(`${icon} ${n.title}`, { duration: 5000 });
+        // Browser notification for calendar reminders
+        if (n.type === 'calendar_reminder' && 'Notification' in window) {
+          const fire = () => new Notification(n.title, { body: n.body || '', icon: '/favicon.ico' });
+          if (Notification.permission === 'granted') {
+            fire();
+          } else if (Notification.permission !== 'denied') {
+            Notification.requestPermission().then(p => { if (p === 'granted') fire(); });
+          }
+        }
       });
     } catch {
       /* silent – server may not be reachable */
@@ -166,6 +175,7 @@ function notificationIcon(type) {
     case 'room_share_added':       return '🔗';
     case 'room_share_removed':     return '🚫';
     case 'federation_invite_received': return '📩';
+    case 'calendar_reminder':      return '🔔';
     default:                       return '🔔';
   }
 }