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

frontend/angular/src/app/features/host/host-shell.component.ts

@@ -0,0 +1,11 @@
+import { Component } from '@angular/core';
+
+@Component({
+  selector: 'app-host-shell',
+  standalone: true,
+  template: `
+    <h2>Host route placeholder</h2>
+    <p>Host flow flyttes hertil i kommende SPA-issues.</p>
+  `,
+})
+export class HostShellComponent {}