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/client-application/tests/client_app_tests.rs

@@ -1,9 +1,8 @@
 use client_application::{ClientApp, RepaintCommand};
 use client_domain::BoundingBox;
 use protocol::{
-    ServerMessage, WidgetDescriptor,
-    WireDisplayHint, WireLayoutNode, WireContainerNode, WireLayoutChild,
-    WireDirection, WireSizing, WireWidgetState, WireKeyValue, WireValue,
+    ServerMessage, WidgetDescriptor, WireContainerNode, WireDirection, WireDisplayHint,
+    WireKeyValue, WireLayoutChild, WireLayoutNode, WireSizing, WireValue, WireWidgetState,
 };
 
 fn screen() -> BoundingBox {
@@ -15,9 +14,10 @@ fn weather_descriptor(id: u16, temp: &str) -> WidgetDescriptor {
         id,
         display_hint: WireDisplayHint::IconValue,
         state: WireWidgetState {
-            data: vec![
-                WireKeyValue { key: "temperature".into(), value: WireValue::String(temp.into()) },
-            ],
+            data: vec![WireKeyValue {
+                key: "temperature".into(),
+                value: WireValue::String(temp.into()),
+            }],
             error: None,
         },
     }
@@ -29,8 +29,14 @@ fn two_widget_layout() -> WireLayoutNode {
         gap: 0,
         padding: 0,
         children: vec![
-            WireLayoutChild { sizing: WireSizing::Flex(1), node: WireLayoutNode::Leaf(1) },
-            WireLayoutChild { sizing: WireSizing::Flex(1), node: WireLayoutNode::Leaf(2) },
+            WireLayoutChild {
+                sizing: WireSizing::Flex(1),
+                node: WireLayoutNode::Leaf(1),
+            },
+            WireLayoutChild {
+                sizing: WireSizing::Flex(1),
+                node: WireLayoutNode::Leaf(2),
+            },
         ],
     })
 }
@@ -116,8 +122,14 @@ fn second_screen_update_repaints_all_widgets_with_new_layout() {
         gap: 0,
         padding: 0,
         children: vec![
-            WireLayoutChild { sizing: WireSizing::Flex(1), node: WireLayoutNode::Leaf(1) },
-            WireLayoutChild { sizing: WireSizing::Flex(1), node: WireLayoutNode::Leaf(2) },
+            WireLayoutChild {
+                sizing: WireSizing::Flex(1),
+                node: WireLayoutNode::Leaf(1),
+            },
+            WireLayoutChild {
+                sizing: WireSizing::Flex(1),
+                node: WireLayoutNode::Leaf(2),
+            },
         ],
     });