[Fix] Virtual Printer proxy mode fails on isolated networks (#757)

When the slicer and printer are on different VLANs, Bambu Studio could
  not send prints through the proxy because the printer's real IP leaked
  through MQTT payloads, the bind protocol forwarded the real printer's
  identity, file transfer and camera ports were not proxied, and FTP
  data connections raced the TLS handshake on zero-byte uploads.

  - Rewrite IP addresses in MQTT PUBLISH payloads (string + integer)
    with proper packet framing and cross-chunk buffering
  - Respond to bind/detect with VP identity via BindServer
  - Add TLS proxies for port 6000 (file transfer) and 322 (RTSP camera)
  - Buffer slicer FTP data during printer connection setup
  - Advertise configured VP name in SSDP proxy
  - Add cross-subnet SSDP wildcard listener for VPN setups
  - Register UserEmailPreference model in models/__init__.py
  - Add 11 unit tests for MQTT rewrite, IP conversion, SSDP name

backend/app/services/virtual_printer/tcp_proxy.py

@@ -540,7 +540,6 @@ class TLSProxy:
                 await writer.drain()
 
                 total_bytes += len(data)
-                logger.debug("%s proxy %s: %s bytes", self.name, direction, len(data))
 
         except asyncio.CancelledError:
             pass  # Expected when the other forwarding direction closes first
@@ -1289,6 +1288,7 @@ class SlicerProxyManager:
     PRINTER_FTP_PORT = 990
     PRINTER_MQTT_PORT = 8883
     PRINTER_FILE_TRANSFER_PORT = 6000
+    PRINTER_RTSP_PORT = 322  # X1/H2/P2 series camera (A1/P1 use port 6000)
     PRINTER_BIND_PORTS = [3000, 3002]
 
     # Local listen ports - must match what Bambu Studio expects
@@ -1328,6 +1328,7 @@ class SlicerProxyManager:
         self._ftp_proxy: TLSProxy | None = None
         self._mqtt_proxy: TLSProxy | None = None
         self._file_transfer_proxy: TLSProxy | None = None
+        self._rtsp_proxy: TLSProxy | None = None
         self._bind_proxies: list[TCPProxy] = []
         self._bind_server = None
         self._tasks: list[asyncio.Task] = []
@@ -1390,6 +1391,21 @@ class SlicerProxyManager:
             bind_address=self.bind_address,
         )
 
+        # RTSP camera proxy — port 322 (TLS)
+        # X1/H2/P2 series use RTSP on port 322 for camera streaming.
+        # A1/P1 series use port 6000 (already proxied via file transfer proxy).
+        self._rtsp_proxy = TLSProxy(
+            name="RTSP",
+            listen_port=self.PRINTER_RTSP_PORT,
+            target_host=self.target_host,
+            target_port=self.PRINTER_RTSP_PORT,
+            server_cert_path=self.cert_path,
+            server_key_path=self.key_path,
+            on_connect=lambda cid: self._log_activity("RTSP", f"connected: {cid}"),
+            on_disconnect=lambda cid: self._log_activity("RTSP", f"disconnected: {cid}"),
+            bind_address=self.bind_address,
+        )
+
         # Bind/auth — respond with VP identity instead of proxying to printer.
         # The detect response contains the printer name, serial, model, and
         # bind status. Proxying it would leak the real printer's identity and
@@ -1453,6 +1469,10 @@ class SlicerProxyManager:
                 run_with_logging(self._file_transfer_proxy),
                 name="slicer_proxy_file_transfer",
             ),
+            asyncio.create_task(
+                run_with_logging(self._rtsp_proxy),
+                name="slicer_proxy_rtsp",
+            ),
         ]
         if self._bind_server:
             self._tasks.append(
@@ -1495,6 +1515,10 @@ class SlicerProxyManager:
             await self._file_transfer_proxy.stop()
             self._file_transfer_proxy = None
 
+        if self._rtsp_proxy:
+            await self._rtsp_proxy.stop()
+            self._rtsp_proxy = None
+
         if self._bind_server:
             await self._bind_server.stop()
             self._bind_server = None