✨ feat(frontend): Storybook + auto-generated Playwright e2e docs with screenshots

Adds three things to make frontend PRs reviewable directly from Gitea web UI:

1. Storybook 8 for Vue 3 components
   - .storybook/main.ts + preview.ts
   - HealthDashboard.stories.ts (1 example story)
   - npm run storybook / npm run build-storybook

2. Playwright JSON reporter + screenshot on every test
   - playwright.config.ts: json reporter + screenshot: 'on'
   - health.spec.ts: explicit screenshot path

3. Auto-generated markdown docs with breadcrumbs
   - scripts/generate-test-docs.mjs: reads results.json -> generates docs/e2e/<test>.md per test
   - docs/README.md: top-level frontend docs index
   - docs/e2e/README.md: e2e index with link to each test
   - Each test markdown has breadcrumb [<- Back to index]
   - Screenshots embedded via relative path

Companion to PR #25 (Nuxt scaffold).

Out of scope (future PRs):
- Visual regression testing
- Storybook deployment / hosted preview
- More e2e test coverage

🤖 Co-Authored-By: Mistral Vibe <vibe@mistral.ai>

frontend/playwright.config.ts

@@ -1,10 +1,19 @@
 import { defineConfig } from '@playwright/test'
+import path from 'path'
+
 export default defineConfig({
   testDir: './tests/e2e',
   timeout: 30_000,
+  reporter: [
+    ['list'],
+    ['json', { outputFile: path.join(process.cwd(), 'test-results', 'results.json') }],
+  ],
   use: {
     baseURL: 'http://localhost:3000',
+    screenshot: 'on',
+    video: 'off',
   },
+  outputDir: 'test-results/output',
   webServer: {
     command: 'npm run dev',
     url: 'http://localhost:3000',