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/bootstrap/Cargo.toml

@@ -10,6 +10,8 @@ config-sqlite.workspace = true
 tcp-server.workspace = true
 http-api.workspace = true
 http-json.workspace = true
+media-adapter.workspace = true
+rss-adapter.workspace = true
 tokio.workspace = true
 anyhow.workspace = true
 tracing.workspace = true