feat(a11y): add axe-core Playwright scorecard for 10 key routes

- Installs @axe-core/playwright at workspace root
- Creates e2e/a11y/scorecard.spec.ts scanning /, /search, /listings/[id],
  /listings/create, /login, /register, /dashboard, /agent/[id],
  /inquiries, /admin/moderation
- API mock layer lets pages render with stubbed JSON so axe sees real DOM
- Critical/serious violations fail the build; moderate/minor are recorded only
- Writes per-route JSON reports to e2e/a11y/reports/ (committed for before/after diffing in PRs)
- Adds dedicated "a11y" Playwright project in playwright.config.ts
- Pre-existing API unit test failures are unrelated to this change

Co-Authored-By: Paperclip <noreply@paperclip.ing>

package.json

@@ -56,6 +56,7 @@
     "seed": "tsx prisma/seed.ts"
   },
   "devDependencies": {
+    "@axe-core/playwright": "^4.11.2",
     "@eslint/js": "^9.39.4",
     "@playwright/test": "^1.59.1",
     "@types/pg": "^8.20.0",