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/media/tests/media_tests.rs

@@ -1,6 +1,6 @@
-use std::time::Duration;
 use domain::{DataSource, DataSourceConfig, DataSourcePort, DataSourceType, Value};
 use media_adapter::MediaAdapter;
+use std::time::Duration;
 
 fn subsonic_response(playing: bool) -> serde_json::Value {
     if playing {
@@ -28,10 +28,10 @@ fn subsonic_response(playing: bool) -> serde_json::Value {
 }
 
 async fn start_fake_subsonic(playing: bool) -> String {
-    let app = axum::Router::new()
-        .route("/rest/getNowPlaying.view", axum::routing::get(move || async move {
-            axum::response::Json(subsonic_response(playing))
-        }));
+    let app = axum::Router::new().route(
+        "/rest/getNowPlaying.view",
+        axum::routing::get(move || async move { axum::response::Json(subsonic_response(playing)) }),
+    );
 
     let listener = tokio::net::TcpListener::bind("127.0.0.1:0").await.unwrap();
     let addr = listener.local_addr().unwrap();
@@ -47,8 +47,11 @@ fn make_source(url: String) -> DataSource {
         poll_interval: Duration::from_secs(5),
         config: DataSourceConfig {
             url: Some(url),
-            headers: vec![],
-            api_key: Some("testtoken".into()),
+            headers: vec![
+                ("username".into(), "test".into()),
+                ("password".into(), "testpass".into()),
+            ],
+            api_key: None,
         },
     }
 }
@@ -62,8 +65,14 @@ async fn returns_now_playing_info() {
     let result = adapter.poll(&source).await.unwrap();
 
     assert_eq!(result.get_path("$.playing"), Some(&Value::Bool(true)));
-    assert_eq!(result.get_path("$.title"), Some(&Value::String("Believer".into())));
-    assert_eq!(result.get_path("$.artist"), Some(&Value::String("Imagine Dragons".into())));
+    assert_eq!(
+        result.get_path("$.title"),
+        Some(&Value::String("Believer".into()))
+    );
+    assert_eq!(
+        result.get_path("$.artist"),
+        Some(&Value::String("Imagine Dragons".into()))
+    );
 }
 
 #[tokio::test]