add SPA config UI, wire media/rss adapters, event-driven layout push

- React SPA: dashboard, data sources CRUD, widgets CRUD, layout builder,
  presets. TanStack Router + Query, shadcn/ui, Vite proxy to :3000
- wire media + rss adapters into polling loop, remove xtb source type
- media adapter: read username/password from headers, proper subsonic auth
- event handler: subscribe to LayoutChanged, push screen update to clients
- fix clippy warnings across workspace (Default impls, collapsible ifs,
  redundant closures, is_none_or, unused imports)

crates/adapters/tcp-server/src/server.rs

@@ -1,10 +1,10 @@
-use std::sync::Arc;
-use tokio::net::TcpListener;
-use tokio::sync::broadcast;
-use tokio::io::AsyncWriteExt;
-use tracing::{info, warn};
 use crate::broadcaster::TcpBroadcaster;
 use crate::error::TcpServerError;
+use std::sync::Arc;
+use tokio::io::AsyncWriteExt;
+use tokio::net::TcpListener;
+use tokio::sync::broadcast;
+use tracing::{info, warn};
 
 pub async fn run_tcp_server(
     addr: &str,