Add IMDb movie importer feature and unify header

Introduces a new movie importer feature allowing admins to search and import movies from IMDb, including new components for search, result display, and error handling. Replaces the schedule header with a reusable menu header component. Updates routing, navigation, and HTTP service to support the new importer. Adds a poster placeholder image and improves poster error handling.

src/app/app-routing-module.ts

@@ -6,6 +6,7 @@ import { MainLayoutComponent } from './layouts/main-layout/main-layout.component
 import { MainComponent } from './main/main.component';
 import { ScheduleComponent } from './schedule/schedule.component';
 import { TheaterOverlayComponent} from './theater-overlay/theater-overlay.component';
+import { MovieImporterComponent } from './movie-importer/movie-importer.component';
 
 const routes: Routes = [
   // Seiten ohne Layout
@@ -19,6 +20,7 @@ const routes: Routes = [
     children: [
       { path: '', component: MainComponent },
       { path: 'schedule', component: ScheduleComponent },
+      { path: 'admin/movie-importer', component: MovieImporterComponent },
       { path: 'theater-overlay', component: TheaterOverlayComponent},
     ],
   },