Refactor stratum server leak handling

[syntaxjak]

Addressing issue: #3867

-Reworked the stratum connection handling into a single ‘handle_connection’ loop using ‘tokio::select!’ To drive reads and writes on the same ‘Frames’ socket.

• Added an RAII ‘WorkerCleanup’ guard so workers are always removed and connections are closed even on errors.
• Simplified the accept loop (no async_stream) and now logs peer addresses when workers connect.

[iho]

Heads-up: #3889 also targets #3867 with the same structural approach (handle_connection + Drop guard + simpler accept loop).

That PR additionally adds idle timeout, max workers, and bounded write queues for the half-open / reconnect-storm failure mode. Worth coordinating so the two don’t land overlapping refactors without combining the resource bounds.