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/detail/detail.component.spec.ts

@@ -2,7 +2,7 @@ import { TestBed } from '@angular/core/testing';
 import { ActivatedRoute, provideRouter, Router } from '@angular/router';
 import { provideHttpClient } from '@angular/common/http';
 import { provideHttpClientTesting } from '@angular/common/http/testing';
-import { of, throwError, Subject } from 'rxjs';
+import { of, throwError, Subject, NEVER } from 'rxjs';
 import { DetailComponent } from './detail.component';
 import { ImageService } from '../services/image.service';
 import { ToastService } from '../services/toast.service';
@@ -113,17 +113,15 @@ describe('DetailComponent', () => {
   });
 
   it('not-found card shown when image is null, loading is false, error is false', () => {
-    const { fixture, component } = setup('img-1', of(MOCK_IMAGE));
-    component.image = null;
-    component.loading = false;
-    component.error = false;
-    fixture.detectChanges();
+    // Service returns null → fetchImage sets image=null, loading=false, markForCheck()
+    const { fixture } = setup('img-1', of(null as any));
     expect((fixture.nativeElement as HTMLElement).querySelector('.not-found-card')).not.toBeNull();
   });
 
   it('tag error element uses danger styling class', () => {
-    const { fixture, component } = setup();
-    component.tagError = 'Invalid tag: special characters not allowed';
+    const { fixture, component, imgSvc } = setup();
+    spyOn(imgSvc, 'updateTags').and.returnValue(throwError(() => ({ error: { detail: 'Invalid tag' } })));
+    component.addTag('bad#tag');
     fixture.detectChanges();
     const errEl = (fixture.nativeElement as HTMLElement).querySelector('.tag-error');
     expect(errEl).not.toBeNull();

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

@@ -1,6 +1,6 @@
 import { TestBed, fakeAsync, tick } from '@angular/core/testing';
 import { ReactiveFormsModule } from '@angular/forms';
-import { Router } from '@angular/router';
+import { ActivatedRoute, Router, convertToParamMap } from '@angular/router';
 import { HttpErrorResponse } from '@angular/common/http';
 import { of, throwError } from 'rxjs';
 import { LoginComponent } from './login.component';
@@ -20,6 +20,7 @@ describe('LoginComponent', () => {
       providers: [
         { provide: AuthService, useValue: authService },
         { provide: Router, useValue: router },
+        { provide: ActivatedRoute, useValue: { snapshot: { queryParamMap: convertToParamMap({}) } } },
       ],
     }).compileComponents();
 

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 {