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/api/src/routes/auth/local.rs

@@ -35,6 +35,7 @@ pub(super) async fn login(
     }
 
     let token = create_jwt(&user, &state)?;
+    let _ = state.activity_log_repo.log("user_login", user.email.as_ref(), None).await;
 
     Ok((
         StatusCode::OK,