feat: Add Palette Editor for Enhanced Color Management

- Introduced a new PaletteEditorWidget for visual editing of dungeon palettes, allowing users to select and modify colors.
- Integrated palette editor into DungeonEditorV2, enabling real-time updates and re-rendering of rooms upon palette changes.
- Enhanced GUI layout to include a dedicated palette editor card, improving user experience and accessibility.
- Implemented callback functionality to notify when palette changes occur, ensuring seamless integration with room rendering.

src/app/gui/widgets/palette_editor_widget.h

@@ -0,0 +1,56 @@
+#ifndef YAZE_APP_GUI_WIDGETS_PALETTE_EDITOR_WIDGET_H
+#define YAZE_APP_GUI_WIDGETS_PALETTE_EDITOR_WIDGET_H
+
+#include <functional>
+#include <vector>
+
+#include "app/gfx/snes_palette.h"
+#include "app/rom.h"
+#include "imgui/imgui.h"
+
+namespace yaze {
+namespace gui {
+
+/**
+ * @brief Simple visual palette editor with color picker
+ * 
+ * Displays dungeon palettes in a grid, allows editing colors,
+ * and notifies when palettes change so rooms can re-render.
+ */
+class PaletteEditorWidget {
+ public:
+  PaletteEditorWidget() = default;
+  
+  void Initialize(Rom* rom);
+  void Draw();
+  
+  // Callback when palette is modified
+  void SetOnPaletteChanged(std::function<void(int palette_id)> callback) {
+    on_palette_changed_ = callback;
+  }
+  
+  // Get/Set current editing palette
+  int current_palette_id() const { return current_palette_id_; }
+  void set_current_palette_id(int id) { current_palette_id_ = id; }
+  
+ private:
+  void DrawPaletteSelector();
+  void DrawColorGrid();
+  void DrawColorPicker();
+  
+  Rom* rom_ = nullptr;
+  int current_palette_id_ = 0;
+  int selected_color_index_ = -1;
+  
+  // Callback for palette changes
+  std::function<void(int palette_id)> on_palette_changed_;
+  
+  // Temp color for editing (RGB 0-1 range for ImGui)
+  ImVec4 editing_color_{0, 0, 0, 1};
+};
+
+}  // namespace gui
+}  // namespace yaze
+
+#endif  // YAZE_APP_GUI_WIDGETS_PALETTE_EDITOR_WIDGET_H
+