Refactor: Remove dynamic port allocation (portsManager) and use single server port for streaming

[iMrShadow]

The current implementation dynamically allocates a new port for every song stream (via portsManager). This is complex, error-prone, and doesn't integrate well with Kubernetes (where only explicitly exposed ports are reachable).

Proposal

• Remove portsManager and all dynamic port assignments.
• Handle all streaming and client-server commands over the main server port.

This will simplify the code and network architecture, improve maintainability and make this project more compatible with cloud deployments.