optimize firebase reads

src/main.ts

@@ -16,6 +16,15 @@ import {FontAwesomeModule} from '@fortawesome/angular-fontawesome';
 import {AppComponent} from './app/app.component';
 import {provideFirebaseApp, initializeApp} from '@angular/fire/app';
 import {provideFirestore, getFirestore} from '@angular/fire/firestore';
+import {UserService} from './app/services/user/user.service';
+
+declare global {
+  interface Window {
+    wgeneratorAdmin?: {
+      rebuildSongUsage(): Promise<unknown>;
+    };
+  }
+}
 
 if (environment.production) {
   enableProdMode();
@@ -42,4 +51,11 @@ bootstrapApplication(AppComponent, {
     {provide: MAT_DATE_LOCALE, useValue: 'de-DE'},
     provideAnimations(),
   ],
-}).catch(err => console.error(err));
+})
+  .then(appRef => {
+    const userService = appRef.injector.get(UserService);
+    window.wgeneratorAdmin = {
+      rebuildSongUsage: () => userService.rebuildSongUsage(),
+    };
+  })
+  .catch(err => console.error(err));