refactor: Update GUI components and integrate new palette widget

- Removed references to the old `EnhancedPaletteEditor` and replaced it with the new `PaletteWidget` across various files, including canvas and context menu implementations.
- Updated CMake configurations to include the new `palette_widget` source files, ensuring proper integration into the build system.
- Refactored GUI code to enhance modularity and maintainability, improving the overall user experience in palette management and editing functionalities.
- Introduced new UI components for background rendering and editor selection dialogs, enhancing the application's graphical interface.

src/app/gui/canvas.h

@@ -12,7 +12,7 @@
 #include "app/gfx/bitmap.h"
 #include "app/rom.h"
 #include "app/gui/canvas_utils.h"
-#include "app/gui/enhanced_palette_editor.h"
+#include "app/gui/widgets/palette_widget.h"
 #include "app/gfx/bpp_format_manager.h"
 #include "app/gui/bpp_format_ui.h"
 #include "app/gui/canvas/canvas_modals.h"
@@ -412,7 +412,7 @@ class Canvas {
   // Modular configuration and state
   CanvasConfig config_;
   CanvasSelection selection_;
-  std::unique_ptr<EnhancedPaletteEditor> palette_editor_;
+  std::unique_ptr<PaletteWidget> palette_editor_;
   
   // Core canvas state
   bool is_hovered_ = false;