feat: add server-sent events for logging and activity tracking

- Implemented a custom tracing layer (`AppLogLayer`) to capture log events and broadcast them to SSE clients.
- Created admin routes for streaming server logs and listing recent activity logs.
- Added an activity log repository interface and SQLite implementation for persisting activity events.
- Integrated activity logging into user authentication and channel CRUD operations.
- Developed frontend components for displaying server logs and activity logs in the admin panel.
- Enhanced the video player with a stats overlay for monitoring streaming metrics.

k-tv-backend/infra/src/activity_log_repository/mod.rs

@@ -0,0 +1,5 @@
+#[cfg(feature = "sqlite")]
+mod sqlite;
+
+#[cfg(feature = "sqlite")]
+pub use sqlite::SqliteActivityLogRepository;