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>

app/app.py

@@ -485,5 +485,7 @@ def trigger_windows_scan():
         })
 
 if __name__ == '__main__':
+    # Get port from environment variable or default to 5000
+    port = int(os.environ.get('FLASK_PORT', 5000))
     # Enable debug mode for development with hot reload
-    app.run(host='0.0.0.0', port=5000, debug=True, use_reloader=True)
+    app.run(host='0.0.0.0', port=port, debug=True, use_reloader=True)