Add proxy mode for virtual printer (cross-LAN slicer support)

Enable Bambu Studio on a remote network to print through BamBuddy
acting as a TLS-terminating proxy for both MQTT and FTP connections.

- Add TLSProxy base class and FTPTLSProxy with PASV response rewriting,
  EPSV→PASV translation, PROT P/C tracking, and one-shot data proxies
- Add SlicerProxyManager to coordinate per-slicer MQTT + FTP proxy pairs
- Support additional SAN IPs in certificate generation for proxy mode
- Broadcast SSDP on LAN B so slicers discover the proxy as a printer
- Narrow FTP passive port range to 50000-50100 with retry logic
- Expose proxy ports (8883, 9990, 50000-50100) in Dockerfile
- Document passive port range in docker-compose.yml

backend/app/services/virtual_printer/tcp_proxy.py

@@ -515,12 +515,6 @@ class FTPTLSProxy(TLSProxy):
 
                     cmd_upper = line.strip().upper()
 
-                    # Log all FTP commands from slicer
-                    try:
-                        logger.info("FTP cmd  >>> %s", line.decode("utf-8", errors="replace"))
-                    except Exception:
-                        pass
-
                     # Replace EPSV with PASV so response includes an IP
                     if cmd_upper == b"EPSV":
                         line = b"PASV"
@@ -593,12 +587,6 @@ class FTPTLSProxy(TLSProxy):
                     line = buffer[:idx]
                     buffer = buffer[idx + 2 :]
 
-                    # Log all FTP responses from printer
-                    try:
-                        logger.info("FTP resp <<< %s", line.decode("utf-8", errors="replace"))
-                    except Exception:
-                        pass
-
                     rewritten = await self._maybe_rewrite_pasv(line, local_ip, session_state)
                     output += rewritten + b"\r\n"