[Docs] Update VP proxy docs, ports, and diagram for #757

- Add ports 6000 (file transfer) and 322 (RTSP camera) to Dockerfile
    EXPOSE and docker-compose.yml bridge mode port mapping
  - Update migration doc with new proxy mode port requirements
  - Regenerate proxy-mode-diagram.png with all proxied ports

Dockerfile

@@ -53,11 +53,13 @@ ENV DATA_DIR=/app/data
 ENV LOG_DIR=/app/logs
 ENV PORT=8000
 
+EXPOSE 322
+EXPOSE 990
 EXPOSE 3000
 EXPOSE 3002
+EXPOSE 6000
 EXPOSE 8000
 EXPOSE 8883
-EXPOSE 990
 EXPOSE 50000-50100
 
 # Health check (uses PORT env var via shell)