[Backend] — Test: `EventsGateway` unauthenticated connections do not join user-specific rooms

[Olowodarey]

Background

EventsGateway.handleConnection joins authenticated clients to user:<sub>
rooms. Unauthenticated connections (no token or invalid token) should not be
added to any user room. There are no tests confirming this behavior.

Goal

Add tests in src/websocket/events.gateway.spec.ts.

Requirements

1. No token: connect a socket without auth.token; assert socket.join
   is NOT called with any user:* room.

2. Invalid token: connect with auth.token = "invalid.jwt.token"; assert
   socket.join not called with user room (JWT verify throws and is caught).

3. Valid token: connect with a valid JWT; assert socket.join is called

Acceptance criteria

• User rooms only joined by authenticated sockets.
• Invalid/missing tokens handled gracefully without crashing.

[gloskull]

Hello, I have 4 years of experience delivering solutions for projects like this, covering backend, frontend, and smart contract development. After carefully reviewing your requirements, I have a clear understanding of the task and am confident in my ability to deliver a clean, efficient, and thoroughly tested solution on time. I prioritize code quality, maintainability, and industry best practices throughout the development process.
My PR will be submitted in under 10hours.