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/channels/schedule.rs

@@ -37,6 +37,8 @@ pub(super) async fn generate_schedule(
         channel_id,
         schedule: schedule.clone(),
     });
+    let detail = format!("{} slots", schedule.slots.len());
+    let _ = state.activity_log_repo.log("schedule_generated", &detail, Some(channel_id)).await;
     Ok((StatusCode::CREATED, Json(ScheduleResponse::from(schedule))))
 }