Fix device popup, mapping, and status-parse defects

- Allow mapping to EMPTY trays only from the multi-machine send page and keep
  both panels pickable in the LEFT_AND_RIGHT view
- Guard the error-dialog cloud snapshot against stale callbacks and fall back
  to the local illustration on timeout
- Parse the ipcam storage-check ack and axis/chamber pushes defensively
- Strip fan-control telemetry, initialize the upgrade error code, restore the
  .json filter in the model-id scan
- Fix best-position popup tray lookup, gradient placement, and colour-list
  ownership
- Cover switch binding sets and invalid-track transients in DevMapping tests

src/slic3r/GUI/DeviceCore/DevUpgrade.h

@@ -60,7 +60,7 @@ private:
     std::map<std::string, DevFirmwareVersionInfo> m_new_ver_list; // some protcols have version list
     DevFirmwareUpgradeState                       m_upgrade_display_state = DevFirmwareUpgradeState::DC;
 
-    int         m_upgrade_err_code;
+    int         m_upgrade_err_code = 0;
     std::string m_upgrade_status;
     std::string m_upgrade_progress;
     std::string m_upgrade_message;