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/Cargo.lock

@@ -90,10 +90,12 @@ dependencies = [
  "thiserror 2.0.17",
  "time",
  "tokio",
+ "tokio-stream",
  "tokio-util",
  "tower",
  "tower-http",
  "tracing",
+ "tracing-subscriber",
  "uuid",
 ]
 
@@ -3546,6 +3548,7 @@ dependencies = [
  "futures-core",
  "pin-project-lite",
  "tokio",
+ "tokio-util",
 ]
 
 [[package]]