feat: implement full authentication system with middleware protection

- Install @supabase/ssr package for server-side auth
- Create middleware.ts for route protection (redirects to login if not authenticated)
- Fix login page admin check to verify specific user ID
- Add AUTH_SETUP.md with complete setup instructions
- Add setup-admin.sql for database configuration
- Logout button already exists in sidebar

admin-web/package.json

@@ -12,6 +12,7 @@
     "test:coverage": "vitest run --coverage"
   },
   "dependencies": {
+    "@supabase/ssr": "^0.9.0",
     "class-variance-authority": "^0.7.1",
     "clsx": "^2.1.1",
     "lucide-react": "^0.576.0",