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/application/tests/data_projection_tests.rs

@@ -1,8 +1,6 @@
-use std::collections::BTreeMap;
-use domain::{
-    DisplayHint, KeyMapping, Value, WidgetConfig, WidgetId, WidgetState,
-};
 use application::DataProjection;
+use domain::{DisplayHint, KeyMapping, Value, WidgetConfig, WidgetId, WidgetState};
+use std::collections::BTreeMap;
 
 fn weather_widget() -> WidgetConfig {
     WidgetConfig::new(
@@ -11,8 +9,14 @@ fn weather_widget() -> WidgetConfig {
         DisplayHint::IconValue,
         10,
         vec![
-            KeyMapping { source_path: "$.temp".into(), target_key: "temperature".into() },
-            KeyMapping { source_path: "$.icon".into(), target_key: "icon".into() },
+            KeyMapping {
+                source_path: "$.temp".into(),
+                target_key: "temperature".into(),
+            },
+            KeyMapping {
+                source_path: "$.icon".into(),
+                target_key: "icon".into(),
+            },
         ],
     )
 }
@@ -33,7 +37,10 @@ fn apply_poll_result_detects_new_widget_state() {
 
     assert_eq!(changed.len(), 1);
     assert_eq!(changed[0].0, 1);
-    assert_eq!(changed[0].1.data.get("temperature"), Some(&Value::Number(5.4)));
+    assert_eq!(
+        changed[0].1.data.get("temperature"),
+        Some(&Value::Number(5.4))
+    );
 }
 
 #[test]
@@ -56,7 +63,10 @@ fn apply_poll_result_detects_changed_value() {
     let changed = projection.apply_poll_result(10, &weather_response(6.1), &widgets);
 
     assert_eq!(changed.len(), 1);
-    assert_eq!(changed[0].1.data.get("temperature"), Some(&Value::Number(6.1)));
+    assert_eq!(
+        changed[0].1.data.get("temperature"),
+        Some(&Value::Number(6.1))
+    );
 }
 
 #[test]
@@ -69,9 +79,10 @@ fn apply_poll_result_only_updates_widgets_bound_to_source() {
             "portfolio".into(),
             DisplayHint::KeyValue,
             20,
-            vec![
-                KeyMapping { source_path: "$.value".into(), target_key: "amount".into() },
-            ],
+            vec![KeyMapping {
+                source_path: "$.value".into(),
+                target_key: "amount".into(),
+            }],
         ),
     ];