test(I2): vitest component smoke tests for high-risk UI

Adds @vue/test-utils + happy-dom and mounts CredentialCard, DownloadEventRow,
PostCard, ActiveDownloadsPanel, QueueStatusBar, asserting they render without
throwing and surface key content — catching the dead-binding / render-error
class (e.g. the last_verified_at regression, guarded explicitly). Vuetify
components are left unresolved (Vue renders unknown elements + slots), so no
Vuetify-plugin setup is needed; only RouterLink is stubbed. Per-file
happy-dom env via docblock keeps the existing node-env specs untouched.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

frontend/test/components/credentialCard.spec.js

@@ -0,0 +1,28 @@
+// @vitest-environment happy-dom
+import { describe, it, expect } from 'vitest'
+
+import CredentialCard from '../../src/components/subscriptions/CredentialCard.vue'
+import { freshPinia, mountComponent } from '../support/mountComponent.js'
+
+const platform = { key: 'patreon', name: 'Patreon', auth_type: 'cookies' }
+
+describe('CredentialCard', () => {
+  it('renders the last-verified row when last_verified is set', () => {
+    // Regression guard: the field was once read as last_verified_at, so the
+    // row silently never rendered.
+    const pinia = freshPinia()
+    const recent = new Date(Date.now() - 2 * 86400_000).toISOString()
+    const credential = {
+      platform: 'patreon', credential_type: 'cookies',
+      captured_at: recent, expires_at: null, last_verified: recent,
+    }
+    const w = mountComponent(CredentialCard, { props: { platform, credential }, pinia })
+    expect(w.text()).toContain('Last verified')
+  })
+
+  it('renders the empty state with no credential', () => {
+    const pinia = freshPinia()
+    const w = mountComponent(CredentialCard, { props: { platform, credential: null }, pinia })
+    expect(w.text()).toContain('No credential stored')
+  })
+})