feat(auth): enhance authentication system with login attempt tracking and configuration options

- Added a new `LoginAttempt` model to track login attempts, including rate limiting and lockout functionality.
- Introduced environment variables for configuring login rate limits and maximum failures.
- Updated the authentication middleware to handle login attempts and enforce rate limits.
- Enhanced the user model with indexing for username and email for improved lookup performance.
- Modified the `.env.example` file to include new optional authentication settings.
- Updated integration tests to cover new login attempt features and authentication state management.

backend/src/__tests__/testUtils.ts

@@ -68,6 +68,7 @@ export const cleanupTestDb = async (prisma: PrismaClient) => {
   });
   await prisma.user.deleteMany({});
   await prisma.systemConfig.deleteMany({});
+  await prisma.loginAttempt.deleteMany({});
 };
 
 /**