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/prisma/migrations/20260120000100_add_user_lookup_indexes/migration.sql

@@ -0,0 +1,5 @@
+-- CreateIndex
+CREATE INDEX "User_username_idx" ON "User"("username");
+
+-- CreateIndex
+CREATE INDEX "User_email_idx" ON "User"("email");