feat(favorites): add EventLike model, favorites API, and notifications module

- EventLike model (user × event unique constraint, indexed)
- contributed_by field on Event (EVT ID or email of community contributor)
- Favorites API endpoints: toggle-like, my-likes, my-liked-events
- Notifications app wired into main urls.py at /api/notifications/
- accounts migration 0014_merge_0013 (resolves split 0013 branches)
- requirements.txt updated

mobile_api/urls.py

@@ -2,6 +2,7 @@ from django.urls import path
 from .views import *
 from mobile_api.views.user import ScheduleCallView
 from mobile_api.views.reviews import ReviewSubmitView, MobileReviewListView, ReviewHelpfulView, ReviewFlagView
+from mobile_api.views.favorites import ToggleLikeView, MyLikedIdsView, MyLikedEventsView
 from ad_control.views import ConsumerFeaturedEventsView, ConsumerTopEventsView
 
 
@@ -39,3 +40,10 @@ urlpatterns += [
     path('reviews/helpful', ReviewHelpfulView.as_view()),
     path('reviews/flag', ReviewFlagView.as_view()),
 ]
+
+# Favorites URLs
+urlpatterns += [
+    path('events/like/', ToggleLikeView.as_view()),
+    path('events/my-likes/', MyLikedIdsView.as_view()),
+    path('events/my-liked-events/', MyLikedEventsView.as_view()),
+]