feat(spa): scaffold Angular app shell with host/player routes

frontend/angular/src/app/app.component.ts

@@ -0,0 +1,20 @@
+import { Component, inject } from '@angular/core';
+import { Router, RouterLink, RouterOutlet } from '@angular/router';
+
+@Component({
+  selector: 'app-root',
+  standalone: true,
+  imports: [RouterOutlet, RouterLink],
+  templateUrl: './app.component.html',
+  styleUrl: './app.component.css',
+})
+export class AppComponent {
+  private readonly router = inject(Router);
+
+  constructor() {
+    const shellRoute = document.body.dataset['wppShellRoute'];
+    if (shellRoute === '/host' || shellRoute === '/player') {
+      void this.router.navigateByUrl(shellRoute);
+    }
+  }
+}