Add support for graceful shutdown on server error

### 🔧 Add Graceful Shutdown

Currently, the server uses:

```go
log.Fatal(http.ListenAndServe(...))
````

This exits immediately on failure. Instead, use `http.Server` with `Shutdown(ctx)` to:

* Allow in-flight requests to complete
* Perform cleanup (e.g., disconnect clients)

👉 Consider using signal handling with `os/signal` for Ctrl+C interrupts.