test: authenticated admin E2E suite + accessibility + visual regression baselines

- Global setup: authenticates as admin, saves storageState for reuse
- playwright.config.ts: 3 projects (setup, authenticated, unauthenticated)
- authenticated-admin.spec.ts: 16 admin pages tested with real auth session
- accessibility.spec.ts: axe-core scans on all admin, public, and portal pages
- visual-regression.spec.ts: dark mode baselines for key pages (toHaveScreenshot)
- @axe-core/playwright added as devDependency
- .gitignore updated: excludes .auth/ and test-results/

Full suite: 262 tests passing (setup:1, authenticated:52, unauthenticated:209)

cannamanage-frontend/package.json

@@ -71,6 +71,7 @@
     "zod": "3.23.8"
   },
   "devDependencies": {
+    "@axe-core/playwright": "^4.11.3",
     "@eslint/compat": "1.2.7",
     "@ianvs/prettier-plugin-sort-imports": "4.4.1",
     "@playwright/test": "^1.60.0",