Add Playwright end-to-end tests for authentication flows and configuration

- Added comprehensive Playwright tests for login, registration, password reset, and authentication guard flows to ensure UI and functional correctness.
- Introduced configuration file `playwright.config.ts` with support for multiple browsers and enhanced debugging settings.
- Verified validation errors, success paths, input state changes, and navigation behavior across authentication components.

frontend/package.json

@@ -39,7 +39,7 @@
     "clsx": "^2.1.1",
     "date-fns": "^4.1.0",
     "lucide-react": "^0.552.0",
-    "next": "15.2.0",
+    "next": "^15.5.6",
     "next-themes": "^0.4.6",
     "react": "^19.0.0",
     "react-dom": "^19.0.0",