feat(device): H2C/A2L device layer

Nozzle rack data model and device-tab panel, multi-nozzle sync, per-nozzle filament blacklist, and print-dispatch nozzle mapping (DevNozzleMappingCtrl V0/V1).

src/slic3r/GUI/DeviceCore/DevUtilBackend.h

@@ -0,0 +1,32 @@
+/**
+ * @file DevUtilBackend.h
+ * @brief Static helpers bridging the backend (slicer/preset) to the device GUI.
+ *
+ * Scope (H2C nozzle rack): exposes only GetNozzleGroupResult — the accessor the print-dispatch
+ * nozzle-mapping V1 request and result-resolve helpers read. Related helpers (per-nozzle info
+ * collection via the ExtruderNozzleInfos/NozzleDef type pair, and the drying-preset lookup) are
+ * not implemented here and left to the consuming code.
+ */
+
+#pragma once
+
+#include "libslic3r/MultiNozzleUtils.hpp"
+
+#include <memory>
+
+namespace Slic3r
+{
+namespace GUI { class Plater; }
+
+class DevUtilBackend
+{
+public:
+    DevUtilBackend() = delete;
+
+    // for rack: the slicer's per-filament -> logical-nozzle grouping for the current plate, read off
+    // the post-slice GCodeProcessorResult (plater->background_process().get_current_gcode_result()).
+    // Returns nullptr when there is no plater / no current result.
+    static std::shared_ptr<MultiNozzleUtils::NozzleGroupResultBase> GetNozzleGroupResult(Slic3r::GUI::Plater* plater);
+};
+
+}; // namespace Slic3r