Fix: Resolve 13 pre-existing UI test failures across Login, Upload, and Detail components

- LoginComponent: provide ActivatedRoute stub (component reads returnUrl query param)
- UploadComponent: add cdr.markForCheck() to handleUploadError so OnPush view updates
  when the method is called directly; fix success test to check showSuccess not toastMessage
- DetailComponent: drive not-found-card and tag-error tests through component methods
  that call markForCheck() rather than directly mutating state on OnPush components

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

ui/src/app/upload/upload.component.spec.ts

@@ -48,7 +48,7 @@ describe('UploadComponent', () => {
     const router = TestBed.inject(Router);
     spyOn(router, 'navigate');
     await component.handleUploadResponse({ id: 'xyz', short_id: 'XyZ12345', duplicate: false } as Parameters<typeof component.handleUploadResponse>[0]);
-    expect(component.toastMessage).toBeTruthy();
+    expect(component.showSuccess).toBeTrue();
     expect(router.navigate).toHaveBeenCalledWith(['/i', 'XyZ12345']);
   });
 

ui/src/app/upload/upload.component.ts

@@ -192,6 +192,7 @@ export class UploadComponent {
     } else {
       this.errorMessage = 'Upload failed. Please try again.';
     }
+    this.cdr.markForCheck();
   }
 
   resetForm(): void {