feat: Add automated testing with Vitest and Playwright

- Install Vitest (integration tests for API routes) and Playwright (E2E tests)
- Add vitest.config.ts, playwright.config.ts, src/test/setup.ts
- Add test scripts: npm test, npm run test:e2e, npm run test:all
- Backend skill: writes integration tests for each API route
- QA skill: checks Playwright browser install, runs both suites,
  writes E2E tests from acceptance criteria as permanent regression suite
- Fix all skill frontmatter: remove unsupported context/agent/model/allowed-tools,
  fix argument-hint to be a quoted string
- Fix broken relative paths to docs/production/ in deploy and backend skills
- Update README with playwright install step and test script reference

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

.claude/skills/frontend/SKILL.md

@@ -1,11 +1,8 @@
 ---
 name: frontend
 description: Build UI components with React, Next.js, Tailwind CSS, and shadcn/ui. Use after architecture is designed.
-argument-hint: [feature-spec-path]
+argument-hint: "feature-spec-path"
 user-invocable: true
-context: fork
-agent: Frontend Developer
-model: opus
 ---
 
 # Frontend Developer