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/components/auth/index.ts

@@ -2,3 +2,5 @@ export { ProtectedRoute } from './ProtectedRoute';
 export { UserProfile } from './UserProfile';
 export { SignInPage } from './SignInPage';
 export { SignUpPage } from './SignUpPage';
+export { NotificationSettings } from './NotificationSettings';
+export type { NotificationPreferences, AreaOfInterest } from './NotificationSettings';