feat: Add configurable port via environment variable

[oritromax]

This PR adds the ability to configure the application's port through an environment variable, making it more flexible for different deployment scenarios.

Changes made:

• Modified Dockerfile to use PORT environment variable (default: 6050)
• Updated run.py to read port from environment variable
• Port can now be configured through docker-compose.yml or docker run command

Example usage:

# docker-compose.yml
services:
  streamdock:
    environment:
      PORT: "6050"  # Custom port

or

docker run -e PORT=6050 ghcr.io/limmer55/streamdock:latest