Implement notification preferences (Task 16)

- Create NotificationSettings component with map-based area selector
- Add radius configuration slider (1-50km range)
- Implement notification type toggles (email, in-app)
- Add notifications tab to user profile page (visible only to profile owner)
- Update backend to parse and return areasOfInterest JSON
- Save and load user notification preferences
- Requirements: 10.1, 10.4

src/services/userService.ts

@@ -5,6 +5,13 @@ import type { User, Report, CleanupEvent } from '@/types';
 export interface UserProfile extends User {
   reportCount: number;
   eventCount: number;
+  notificationEmail: boolean;
+  notificationInApp: boolean;
+  areasOfInterest: Array<{
+    lat: number;
+    lng: number;
+    radius: number;
+  }>;
 }
 
 export interface UserActivity {