Add flexible Flask port configuration via environment variable

- Add FLASK_PORT environment variable support in docker-compose.yml
- Update Flask app to read port from FLASK_PORT environment variable
- Add FLASK_PORT configuration to .env and .env.example files
- Enables running Flask on custom ports to avoid port conflicts in containerized environments

🤖 Generated with [Claude Code](https://claude.ai/code)

Co-Authored-By: Claude <noreply@anthropic.com>

docker-compose.yml

@@ -15,6 +15,7 @@ services:
       - PYTHONUNBUFFERED=1
       - WSL_INTEROP=${WSL_INTEROP}
       - FLASK_DEBUG=${FLASK_DEBUG:-false}
+      - FLASK_PORT=${FLASK_PORT:-5000}
     network_mode: "${WOL_NETWORK_MODE:-bridge}"
     privileged: true
     cap_add: