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/src/lib.rs

@@ -1,19 +1,17 @@
 #![allow(async_fn_in_trait)]
 
 pub mod entities;
-pub mod value_objects;
 pub mod events;
 pub mod ports;
+pub mod value_objects;
 
 pub use entities::{
-    WidgetConfig, WidgetId,
-    DataSource, DataSourceId, DataSourceType, DataSourceConfig, DataSourceValidationError,
-    LayoutPreset, LayoutPresetId,
-};
-pub use value_objects::{
-    Value, KeyMapping,
-    WidgetState, WidgetError, DisplayHint,
-    Layout, LayoutNode, LayoutChild, ContainerNode, Direction, Sizing, LayoutValidationError,
+    DataSource, DataSourceConfig, DataSourceId, DataSourceType, DataSourceValidationError,
+    LayoutPreset, LayoutPresetId, WidgetConfig, WidgetId,
 };
 pub use events::DomainEvent;
-pub use ports::{ConfigRepository, DataSourcePort, BroadcastPort, EventPublisher};
+pub use ports::{BroadcastPort, ConfigRepository, DataSourcePort, EventPublisher};
+pub use value_objects::{
+    ContainerNode, Direction, DisplayHint, KeyMapping, Layout, LayoutChild, LayoutNode,
+    LayoutValidationError, Sizing, Value, WidgetError, WidgetState,
+};