Merge upstream main: Python plugins, Bambu device rework, macOS fixes

Resolved 4 conflicts:
- PrintConfig.hpp / Preset.cpp: upstream restored calib_flowrate_topinfill_special_order
  (removed in the prior merge, now re-added and re-registered); kept it alongside our
  IMEX options (imex_parallel_mode, imex_head_filament_map).
- Plater.cpp: kept our <sstream> include plus upstream's <optional> and plugin includes.
- tests/fff_print/test_gcodewriter.cpp: both sides appended disjoint scenarios after a
  shared base. Reconstructed as upstream's full file (base + its 3 toolchange/H2C
  scenarios + the boost/filesystem include its helper needs) followed by our 10
  set_pressure_advance / set_temperature scenarios. 22 scenarios total, no duplicates.

src/slic3r/GUI/GCodeViewer.cpp

@@ -448,7 +448,7 @@ void GCodeViewer::SequentialView::Marker::render_position_window(const libvgcode
             add_row(_u8L("Flow rate"), buff);
             sprintf(buff, "%.0f %%", vertex.fan_speed);
             add_row(_u8L("Fan speed"), buff);
-            sprintf(buff, ("%.0f " + _u8L("°C")).c_str(), vertex.temperature);
+            sprintf(buff, ("%.0f " + _u8L("\u2103" /* °C */)).c_str(), vertex.temperature);
             add_row(_u8L("Temperature"), buff);
             sprintf(buff, "%.4f", vertex.pressure_advance);
             add_row(_u8L("Pressure Advance"), buff);
@@ -4083,7 +4083,7 @@ void GCodeViewer::render_legend(float &legend_height, int canvas_width, int canv
         break;
     }
     case libvgcode::EViewType::FanSpeed:       { imgui.title(_u8L("Fan speed (%)")); break; }
-    case libvgcode::EViewType::Temperature:    { imgui.title(_u8L("Temperature (°C)")); break; }
+    case libvgcode::EViewType::Temperature:    { imgui.title(_u8L("Temperature (℃)")); break; }
 // ORCA: Add Pressure Advance visualization support
     case libvgcode::EViewType::PressureAdvance:{ imgui.title(_u8L("Pressure Advance")); break; }
     case libvgcode::EViewType::VolumetricFlowRate: