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/protocol/tests/conversion_tests.rs

@@ -1,24 +1,24 @@
-use std::collections::BTreeMap;
 use domain::{
-    Value, WidgetState, WidgetError, DisplayHint,
-    LayoutNode, ContainerNode, LayoutChild, Direction, Sizing,
+    ContainerNode, Direction, DisplayHint, LayoutChild, LayoutNode, Sizing, Value, WidgetError,
+    WidgetState,
 };
 use protocol::{
-    WireValue, WireWidgetState, WireWidgetError, WireDisplayHint,
-    WireLayoutNode, WireContainerNode, WireLayoutChild, WireDirection, WireSizing,
-    WireKeyValue,
+    WireContainerNode, WireDirection, WireDisplayHint, WireKeyValue, WireLayoutChild,
+    WireLayoutNode, WireSizing, WireValue, WireWidgetError, WireWidgetState,
 };
+use std::collections::BTreeMap;
 
 #[test]
 fn value_converts_to_wire_and_back() {
-    let original = Value::Object(BTreeMap::from([
-        ("items".into(), Value::Array(vec![
+    let original = Value::Object(BTreeMap::from([(
+        "items".into(),
+        Value::Array(vec![
             Value::String("hello".into()),
             Value::Number(42.0),
             Value::Bool(true),
             Value::Null,
-        ])),
-    ]));
+        ]),
+    )]));
 
     let wire: WireValue = (&original).into();
     let roundtripped: Value = wire.into();
@@ -28,9 +28,7 @@ fn value_converts_to_wire_and_back() {
 #[test]
 fn widget_state_with_error_converts_to_wire_and_back() {
     let original = WidgetState {
-        data: BTreeMap::from([
-            ("temp".into(), Value::Number(5.4)),
-        ]),
+        data: BTreeMap::from([("temp".into(), Value::Number(5.4))]),
         error: Some(WidgetError::SourceUnavailable),
     };
 
@@ -56,12 +54,10 @@ fn layout_tree_converts_to_wire_and_back() {
                     direction: Direction::Column,
                     gap: 2,
                     padding: 0,
-                    children: vec![
-                        LayoutChild {
-                            sizing: Sizing::Flex(1),
-                            node: LayoutNode::Leaf(2),
-                        },
-                    ],
+                    children: vec![LayoutChild {
+                        sizing: Sizing::Flex(1),
+                        node: LayoutNode::Leaf(2),
+                    }],
                 }),
             },
         ],
@@ -74,7 +70,11 @@ fn layout_tree_converts_to_wire_and_back() {
 
 #[test]
 fn display_hint_converts_to_wire_and_back() {
-    for hint in [DisplayHint::IconValue, DisplayHint::TextBlock, DisplayHint::KeyValue] {
+    for hint in [
+        DisplayHint::IconValue,
+        DisplayHint::TextBlock,
+        DisplayHint::KeyValue,
+    ] {
         let wire: WireDisplayHint = (&hint).into();
         let roundtripped: DisplayHint = wire.into();
         assert_eq!(hint, roundtripped);