feat(m5): notifications & activity log foundation

- Expand NotificationRepository (unread list paginated, count, markRead
  ownership-scoped); new ActivityLogRepository (create, findByProject
  paginated) with deterministic created_at+id ordering
- NotificationService (notifyOnEvent, resolveTargets for 8 event types,
  injectable SseBroadcaster for M8) + ActivityLogService (logActivity,
  listByProject)
- NotificationEvent/SseEvent/SseBroadcaster types in lib/types
- APIs: GET /api/notifications, POST /api/notifications/:id/read,
  GET /api/projects/:projectId/activity
- Screens: notifications list + MarkReadButton, NotificationBadge in
  Header, project activity page + ProjectNav link
- Unit tests for both repositories and services (28 new)

lib/api/services.ts

@@ -2,8 +2,11 @@ import { getDb } from '@/lib/db/sqlite';
 import { ProjectRepository } from '@/repositories/ProjectRepository';
 import { ProjectMemberRepository } from '@/repositories/ProjectMemberRepository';
 import { NotificationRepository } from '@/repositories/NotificationRepository';
+import { ActivityLogRepository } from '@/repositories/ActivityLogRepository';
 import { UserRepository } from '@/repositories/UserRepository';
 import { ProjectService } from '@/services/ProjectService';
+import { NotificationService } from '@/services/NotificationService';
+import { ActivityLogService } from '@/services/ActivityLogService';
 
 /**
  * Route Handler用に各Repository/Serviceを構築するファクトリ。
@@ -19,6 +22,14 @@ export function createProjectService(): ProjectService {
   );
 }
 
+export function createNotificationService(): NotificationService {
+  return new NotificationService(new NotificationRepository(getDb()));
+}
+
+export function createActivityLogService(): ActivityLogService {
+  return new ActivityLogService(new ActivityLogRepository(getDb()));
+}
+
 export function createUserRepository(): UserRepository {
   return new UserRepository(getDb());
 }