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-domain/src/ports/display.rs

@@ -4,7 +4,13 @@ pub trait DisplayPort {
     type Error;
 
     fn clear_region(&mut self, bounds: BoundingBox) -> Result<(), Self::Error>;
-    fn draw_text(&mut self, text: &str, x: u16, y: u16, bounds: BoundingBox) -> Result<(), Self::Error>;
+    fn draw_text(
+        &mut self,
+        text: &str,
+        x: u16,
+        y: u16,
+        bounds: BoundingBox,
+    ) -> Result<(), Self::Error>;
     fn draw_icon(&mut self, icon: &str, x: u16, y: u16) -> Result<(), Self::Error>;
     fn fill_background(&mut self, bounds: BoundingBox) -> Result<(), Self::Error>;
     fn flush(&mut self) -> Result<(), Self::Error>;