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/lib.rs

@@ -1,6 +1,6 @@
 pub mod error;
-mod serialization;
 mod repository;
+mod serialization;
 
 use sqlx::SqlitePool;
 
@@ -27,8 +27,10 @@ impl SqliteConfigStore {
                 data_source_id INTEGER NOT NULL,
                 mappings TEXT NOT NULL,
                 max_data_size INTEGER NOT NULL
-            )"
-        ).execute(&self.pool).await?;
+            )",
+        )
+        .execute(&self.pool)
+        .await?;
 
         sqlx::query(
             "CREATE TABLE IF NOT EXISTS data_sources (
@@ -37,23 +39,29 @@ impl SqliteConfigStore {
                 source_type TEXT NOT NULL,
                 poll_interval_secs INTEGER NOT NULL,
                 config TEXT NOT NULL
-            )"
-        ).execute(&self.pool).await?;
+            )",
+        )
+        .execute(&self.pool)
+        .await?;
 
         sqlx::query(
             "CREATE TABLE IF NOT EXISTS layout (
                 id INTEGER PRIMARY KEY CHECK (id = 1),
                 data TEXT NOT NULL
-            )"
-        ).execute(&self.pool).await?;
+            )",
+        )
+        .execute(&self.pool)
+        .await?;
 
         sqlx::query(
             "CREATE TABLE IF NOT EXISTS presets (
                 id INTEGER PRIMARY KEY,
                 name TEXT NOT NULL,
                 layout_data TEXT NOT NULL
-            )"
-        ).execute(&self.pool).await?;
+            )",
+        )
+        .execute(&self.pool)
+        .await?;
 
         Ok(())
     }