feat: add testing infrastructure — Vitest, Playwright, CI, git hooks

Add comprehensive testing covering 420 unit/handler tests across 24 Vitest
files, 9 Playwright E2E specs, accessibility scans, and visual regression.
Includes GitHub Actions CI, Husky pre-push hook, and TESTING.md docs.

package.json

@@ -9,7 +9,15 @@
     "preview": "nuxt preview",
     "postinstall": "nuxt prepare",
     "test": "vitest",
-    "test:run": "vitest run"
+    "test:run": "vitest run",
+    "test:e2e": "npx playwright test",
+    "test:e2e:ui": "npx playwright test --ui",
+    "test:e2e:headed": "npx playwright test --headed",
+    "test:visual": "npx playwright test e2e/visual/",
+    "test:visual:update": "npx playwright test e2e/visual/ --update-snapshots",
+    "test:a11y": "npx playwright test e2e/a11y.spec.js",
+    "test:all": "npm run test:run && npx playwright test",
+    "prepare": "husky"
   },
   "dependencies": {
     "@cloudinary/vue": "^1.13.3",
@@ -37,10 +45,13 @@
     "zod": "^4.1.3"
   },
   "devDependencies": {
+    "@axe-core/playwright": "^4.11.1",
     "@nuxt/test-utils": "^4.0.0",
+    "@playwright/test": "^1.59.1",
     "@tailwindcss/typography": "^0.5.19",
     "@types/jsonwebtoken": "^9.0.10",
     "@types/oidc-provider": "^9.5.0",
+    "husky": "^9.1.7",
     "jsdom": "^28.1.0",
     "vitest": "^4.0.18"
   }