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/mod.rs

@@ -5,6 +5,7 @@
 use crate::state::AppState;
 use axum::Router;
 
+pub mod admin;
 pub mod auth;
 pub mod channels;
 pub mod config;
@@ -15,6 +16,7 @@ pub mod library;
 /// Construct the API v1 router
 pub fn api_v1_router() -> Router<AppState> {
     Router::new()
+        .nest("/admin", admin::router())
         .nest("/auth", auth::router())
         .nest("/channels", channels::router())
         .nest("/config", config::router())