✨ 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/package.json

@@ -6,12 +6,20 @@
     "dev": "nuxt dev",
     "generate": "nuxt generate",
     "preview": "nuxt preview",
-    "postinstall": "nuxt prepare"
+    "postinstall": "nuxt prepare",
+    "storybook": "storybook dev -p 6006",
+    "build-storybook": "storybook build",
+    "docs:gen": "playwright test && node scripts/generate-test-docs.mjs",
+    "docs:full": "npm run build-storybook && npm run docs:gen"
   },
   "devDependencies": {
     "@playwright/test": "^1.59.1",
+    "@storybook/addon-essentials": "^8.0.0",
+    "@storybook/vue3": "^8.0.0",
+    "@storybook/vue3-vite": "^8.0.0",
     "@types/node": "^25.6.0",
     "nuxt": "^3.13.0",
+    "storybook": "^8.0.0",
     "typescript": "^6.0.3"
   },
   "packageManager": "npm@11.5.2"