Show the print-failure snapshot in the device error dialog

When a print fails, DeviceErrorDialog now fetches the printer's captured camera
frame of the failure and shows it in place of the generic HMS illustration,
falling back to the local image and a drawn placeholder on older plugins or errors.

- Agent: add get_hms_snapshot through NetworkAgent / IPrinterAgent (BBL calls the
  bound plugin symbol; other agents no-op, so old plugins degrade gracefully).
- DeviceManager: parse and clear m_print_error_img_id from the print-error message.
- Dialog: tiered cloud/local/placeholder image reusing the single image widget,
  with a liveness-guarded async callback decoded on the UI thread.

src/slic3r/Utils/BBLPrinterAgent.cpp

@@ -171,6 +171,19 @@ int BBLPrinterAgent::request_bind_ticket(std::string* ticket)
     return -1;
 }
 
+int BBLPrinterAgent::get_hms_snapshot(std::string dev_id, std::string file_name, std::function<void(std::string, int)> callback)
+{
+    auto& plugin = BBLNetworkPlugin::instance();
+    auto agent = plugin.get_agent();
+    auto func = plugin.get_get_hms_snapshot();
+    // dev_id/file_name are passed as lvalues to bind the plugin's std::string& params.
+    // A null func (older plugin without this symbol) falls through to -1 so callers degrade gracefully.
+    if (func && agent) {
+        return func(agent, dev_id, file_name, callback);
+    }
+    return -1;
+}
+
 int BBLPrinterAgent::set_server_callback(OnServerErrFn fn)
 {
     auto& plugin = BBLNetworkPlugin::instance();

src/slic3r/Utils/BBLPrinterAgent.hpp

@@ -45,6 +45,7 @@ public:
     int bind(std::string dev_ip, std::string dev_id, std::string dev_model, std::string sec_link, std::string timezone, bool improved, OnUpdateStatusFn update_fn) override;
     int unbind(std::string dev_id) override;
     int request_bind_ticket(std::string* ticket) override;
+    int get_hms_snapshot(std::string dev_id, std::string file_name, std::function<void(std::string, int)> callback) override;
     int set_server_callback(OnServerErrFn fn) override;
 
     // Machine Selection

src/slic3r/Utils/IPrinterAgent.hpp

@@ -139,6 +139,12 @@ public:
      */
     virtual int request_bind_ticket(std::string* ticket) = 0;
 
+    /**
+     * Fetch the cloud snapshot image captured at a print failure.
+     * Returns 0 if the request was dispatched; the image body arrives via callback(body, http_status).
+     */
+    virtual int get_hms_snapshot(std::string dev_id, std::string file_name, std::function<void(std::string, int)> callback) = 0;
+
     /**
      * Register callback for fatal HTTP errors.
      */

src/slic3r/Utils/MoonrakerPrinterAgent.cpp

@@ -254,6 +254,15 @@ int MoonrakerPrinterAgent::request_bind_ticket(std::string* ticket)
     return BAMBU_NETWORK_SUCCESS;
 }
 
+int MoonrakerPrinterAgent::get_hms_snapshot(std::string dev_id, std::string file_name, std::function<void(std::string, int)> callback)
+{
+    // No BBL cloud snapshot source; report failure so the caller falls back.
+    (void) dev_id;
+    (void) file_name;
+    (void) callback;
+    return -1;
+}
+
 int MoonrakerPrinterAgent::set_server_callback(OnServerErrFn fn)
 {
     std::lock_guard<std::recursive_mutex> lock(state_mutex);

src/slic3r/Utils/MoonrakerPrinterAgent.hpp

@@ -45,6 +45,7 @@ public:
     int bind(std::string dev_ip, std::string dev_id, std::string dev_model, std::string sec_link, std::string timezone, bool improved, OnUpdateStatusFn update_fn) override;
     int unbind(std::string dev_id) override;
     int request_bind_ticket(std::string* ticket) override;
+    int get_hms_snapshot(std::string dev_id, std::string file_name, std::function<void(std::string, int)> callback) override;
     int set_server_callback(OnServerErrFn fn) override;
 
     // Machine Selection

src/slic3r/Utils/NetworkAgent.cpp

@@ -937,4 +937,11 @@ int NetworkAgent::request_bind_ticket(std::string* ticket)
     return -1;
 }
 
+int NetworkAgent::get_hms_snapshot(std::string dev_id, std::string file_name, std::function<void(std::string, int)> callback)
+{
+    if (m_printer_agent)
+        return m_printer_agent->get_hms_snapshot(dev_id, file_name, callback);
+    return -1;
+}
+
 } // namespace Slic3r

src/slic3r/Utils/NetworkAgent.hpp

@@ -166,6 +166,7 @@ public:
     FilamentSyncMode get_filament_sync_mode() const;
     bool fetch_filament_info(std::string dev_id);
     int request_bind_ticket(std::string* ticket);
+    int get_hms_snapshot(std::string dev_id, std::string file_name, std::function<void(std::string, int)> callback);
 
 private:
     struct PrinterCallbacks {

src/slic3r/Utils/OrcaPrinterAgent.cpp

@@ -95,6 +95,15 @@ int OrcaPrinterAgent::request_bind_ticket(std::string* ticket)
     return BAMBU_NETWORK_SUCCESS;
 }
 
+int OrcaPrinterAgent::get_hms_snapshot(std::string dev_id, std::string file_name, std::function<void(std::string, int)> callback)
+{
+    // No BBL cloud snapshot source; report failure so the caller falls back.
+    (void) dev_id;
+    (void) file_name;
+    (void) callback;
+    return -1;
+}
+
 int OrcaPrinterAgent::set_server_callback(OnServerErrFn fn)
 {
     std::lock_guard<std::mutex> lock(state_mutex);

src/slic3r/Utils/OrcaPrinterAgent.hpp

@@ -45,6 +45,7 @@ public:
     int bind(std::string dev_ip, std::string dev_id, std::string dev_model, std::string sec_link, std::string timezone, bool improved, OnUpdateStatusFn update_fn) override;
     int unbind(std::string dev_id) override;
     int request_bind_ticket(std::string* ticket) override;
+    int get_hms_snapshot(std::string dev_id, std::string file_name, std::function<void(std::string, int)> callback) override;
     int set_server_callback(OnServerErrFn fn) override;
 
     // Machine Selection