feat: add initial Socket.IO queue server implementation

- Created a basic Socket.IO server that manages user connections and queues for events.
- Implemented queue logic to handle concurrent user limits and JWT token issuance.
- Added MySQL configuration for potential persistence of queue positions.
- Introduced environment variables for configuration through a .env.example file.

.env.example

@@ -0,0 +1,17 @@
+# Socket server
+SOCKET_PORT=4000
+NEXT_PUBLIC_SOCKET_URL=http://localhost:4000
+
+# Queue settings
+QUEUE_THRESHOLD=100
+CONCURRENT_ACTIVE=50
+TOKEN_TTL_SECONDS=900
+
+# JWT
+JWT_SECRET=your_jwt_secret_here
+
+# MySQL (optional)
+MYSQL_HOST=localhost
+MYSQL_USER=root
+MYSQL_PASSWORD=yourpassword
+MYSQL_DATABASE=queue_demo