Remove Unused Project Includes and Forward-Declare Where a Type Is Only Referenced

Generated with include-what-you-use and applied conservatively. Only OrcaSlicer's own headers, the ones under src/ and tests/, are removed or forward-declared; standard-library and third-party includes are left alone. An include is removed only when both the Release and the Debug configuration leave it unused, never from inside a conditional block, and never from a file with platform-specific blocks, which only gain includes. Files whose only use of a header sits behind a feature or debug macro (libvgcode's OpenGL ES and marker code, the ARACHNE/TESTS_EXPORT_SVGS debug output) keep their includes.

clonable_ptr.hpp gains #pragma once; it had no include guard and was only safe while Config.hpp was its sole includer.

src/slic3r/GUI/CAD/DesignPanel.cpp

@@ -88,7 +88,6 @@
 #include "slic3r/GUI/wxExtensions.hpp"   // ScalableButton, create_scaled_bitmap
 #include "slic3r/GUI/Widgets/Label.hpp"             // HarmonyOS Sans fonts (Head_*/Body_*) shared with the rest of Orca
 #include "slic3r/GUI/Widgets/DropDown.hpp"          // Orca-themed combo dropdown (white/teal selector) for the tool flyouts
-#include "slic3r/GUI/Widgets/Button.hpp"            // Orca-styled Button (ButtonStyle/ButtonType) — same look as Prepare
 #include "slic3r/GUI/Widgets/CheckBox.hpp"          // Orca teal check (label lives in the row's left column)
 #include "slic3r/GUI/Widgets/ComboBox.hpp"          // Orca dropdown — replaces wxChoice in every Design card
 #include "slic3r/GUI/Widgets/StaticBox.hpp"         // Prepare's rounded white card frame around each tool dialog
@@ -100,6 +99,7 @@
 #include "libslic3r/BuildVolume.hpp"
 #include "slic3r/GUI/MainFrame.hpp"
 #include "slic3r/GUI/GUI_ObjectList.hpp"
+#include "slic3r/GUI/I18N.hpp"
 
 // English-only pin for the Design tab (see design-ux-contract): one lever
 // de-translates this whole TU so our strings never half-translate against the host's