feat(notifications): add delete functionality for individual and all notifications

feat(guest-join): support access code in guest join URL

src/contexts/NotificationContext.jsx

@@ -71,8 +71,29 @@ export function NotificationProvider({ children }) {
     } catch { /* silent */ }
   };
 
+  const deleteNotification = async (id) => {
+    try {
+      await api.delete(`/notifications/${id}`);
+      setNotifications(prev => {
+        const removed = prev.find(n => n.id === id);
+        if (removed && !removed.read) setUnreadCount(c => Math.max(0, c - 1));
+        return prev.filter(n => n.id !== id);
+      });
+      seenIds.current.delete(id);
+    } catch { /* silent */ }
+  };
+
+  const clearAll = async () => {
+    try {
+      await api.delete('/notifications/all');
+      setNotifications([]);
+      setUnreadCount(0);
+      seenIds.current = new Set();
+    } catch { /* silent */ }
+  };
+
   return (
-    <NotificationContext.Provider value={{ notifications, unreadCount, markRead, markAllRead, refresh: fetch }}>
+    <NotificationContext.Provider value={{ notifications, unreadCount, markRead, markAllRead, deleteNotification, clearAll, refresh: fetch }}>
       {children}
     </NotificationContext.Provider>
   );