fix: point check-in QR links to frontend page

frontend/src/app/pages/check-in-placeholder-page.component.ts

@@ -11,7 +11,7 @@ import {
 } from '@angular/core';
 import { takeUntilDestroyed } from '@angular/core/rxjs-interop';
 import { FormBuilder, ReactiveFormsModule, Validators } from '@angular/forms';
-import { RouterLink } from '@angular/router';
+import { ActivatedRoute, RouterLink } from '@angular/router';
 import { MatButtonModule } from '@angular/material/button';
 import { MatCardModule } from '@angular/material/card';
 import { MatFormFieldModule } from '@angular/material/form-field';
@@ -326,6 +326,7 @@ type BarcodeDetectorConstructor = new (options?: { formats?: string[] }) => Barc
 export class CheckInPlaceholderPageComponent {
   private readonly destroyRef = inject(DestroyRef);
   private readonly formBuilder = inject(FormBuilder);
+  private readonly route = inject(ActivatedRoute);
   private readonly showsApi = inject(ShowsApiService);
   private readonly barcodeDetectorCtor = (globalThis as { BarcodeDetector?: BarcodeDetectorConstructor }).BarcodeDetector;
   private readonly scannerSupported =
@@ -358,6 +359,12 @@ export class CheckInPlaceholderPageComponent {
 
   constructor() {
     this.destroyRef.onDestroy(() => this.stopScanner());
+    const tokenFromQuery = this.route.snapshot.queryParamMap.get('token')?.trim() ?? '';
+    if (tokenFromQuery) {
+      this.tokenForm.controls.token.setValue(tokenFromQuery);
+      this.tokenForm.controls.token.markAsTouched();
+      this.preview();
+    }
   }
 
   protected preview(): void {