refactor(webui): route stats interop through shell bridge

- move stats route legacy handoffs onto explicit SoulSyncWebShellBridge methods\n- stop relying on ad hoc window globals from React code for artist navigation and playback\n- update shell bridge tests and route test doubles to enforce the expanded bridge contract

webui/src/platform/shell/globals.d.ts

@@ -62,28 +62,6 @@ declare global {
       showLoadingOverlay: (message?: string) => void;
       hideLoadingOverlay: () => void;
     };
-    navigateToArtistDetail?: (
-      artistId: string | number,
-      artistName: string,
-      sourceOverride?: string | null,
-      options?: Record<string, unknown>,
-    ) => void;
-    playLibraryTrack?: (
-      track: {
-        id: string | number;
-        title: string;
-        file_path: string;
-        bitrate?: string | number | null;
-        artist_id?: string | number | null;
-        album_id?: string | number | null;
-        _stats_image?: string | null;
-      },
-      albumTitle: string,
-      artistName: string,
-    ) => void | Promise<void>;
-    startStream?: (searchResult: Record<string, unknown>) => void | Promise<void>;
-    showLoadingOverlay?: (message?: string) => void;
-    hideLoadingOverlay?: () => void;
   }
 }