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/adapters/config-sqlite/src/repository/widgets.rs

@@ -1,10 +1,13 @@
-use domain::{WidgetConfig, WidgetId};
 use crate::SqliteConfigStore;
 use crate::error::SqliteConfigError;
 use crate::serialization::widget as ser;
+use domain::{WidgetConfig, WidgetId};
 
 impl SqliteConfigStore {
-    pub(crate) async fn get_widget_impl(&self, id: WidgetId) -> Result<Option<WidgetConfig>, SqliteConfigError> {
+    pub(crate) async fn get_widget_impl(
+        &self,
+        id: WidgetId,
+    ) -> Result<Option<WidgetConfig>, SqliteConfigError> {
         let row = sqlx::query("SELECT * FROM widgets WHERE id = ?")
             .bind(id as i64)
             .fetch_optional(&self.pool)
@@ -23,10 +26,13 @@ impl SqliteConfigStore {
             .await
             .map_err(SqliteConfigError::Sql)?;
 
-        rows.iter().map(|r| ser::widget_from_row(r)).collect()
+        rows.iter().map(ser::widget_from_row).collect()
     }
 
-    pub(crate) async fn save_widget_impl(&self, config: &WidgetConfig) -> Result<(), SqliteConfigError> {
+    pub(crate) async fn save_widget_impl(
+        &self,
+        config: &WidgetConfig,
+    ) -> Result<(), SqliteConfigError> {
         let mappings_json = ser::mappings_to_json(&config.mappings)?;
         let hint_str = ser::display_hint_to_str(&config.display_hint);