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/domain/tests/value_tests.rs

@@ -1,5 +1,5 @@
-use std::collections::BTreeMap;
 use domain::Value;
+use std::collections::BTreeMap;
 
 #[test]
 fn estimated_size_of_string_is_its_byte_length() {
@@ -29,37 +29,31 @@ fn estimated_size_of_nested_structure_sums_recursively() {
 
 #[test]
 fn estimated_size_of_array_sums_elements() {
-    let v = Value::Array(vec![
-        Value::String("abc".into()),
-        Value::Number(1.0),
-    ]);
+    let v = Value::Array(vec![Value::String("abc".into()), Value::Number(1.0)]);
     assert_eq!(v.estimated_size(), 11);
 }
 
 #[test]
 fn get_path_returns_none_for_missing_key() {
-    let data = Value::Object(BTreeMap::from([
-        ("main".into(), Value::Number(1.0)),
-    ]));
+    let data = Value::Object(BTreeMap::from([("main".into(), Value::Number(1.0))]));
     assert_eq!(data.get_path("$.missing"), None);
 }
 
 #[test]
 fn get_path_returns_none_when_traversing_non_object() {
-    let data = Value::Object(BTreeMap::from([
-        ("temp".into(), Value::Number(5.4)),
-    ]));
+    let data = Value::Object(BTreeMap::from([("temp".into(), Value::Number(5.4))]));
     assert_eq!(data.get_path("$.temp.nested"), None);
 }
 
 #[test]
 fn get_path_accesses_array_by_index() {
-    let data = Value::Object(BTreeMap::from([
-        ("items".into(), Value::Array(vec![
+    let data = Value::Object(BTreeMap::from([(
+        "items".into(),
+        Value::Array(vec![
             Value::String("first".into()),
             Value::String("second".into()),
-        ])),
-    ]));
+        ]),
+    )]));
     assert_eq!(
         data.get_path("$.items[1]"),
         Some(&Value::String("second".into()))
@@ -68,10 +62,9 @@ fn get_path_accesses_array_by_index() {
 
 #[test]
 fn get_path_traverses_nested_object() {
-    let data = Value::Object(BTreeMap::from([
-        ("main".into(), Value::Object(BTreeMap::from([
-            ("temp".into(), Value::Number(5.4)),
-        ]))),
-    ]));
+    let data = Value::Object(BTreeMap::from([(
+        "main".into(),
+        Value::Object(BTreeMap::from([("temp".into(), Value::Number(5.4))])),
+    )]));
     assert_eq!(data.get_path("$.main.temp"), Some(&Value::Number(5.4)));
 }