feat: Enhance SettingsEditor with new features and UI improvements

- Added new tabs for Theme Management, Editor Behavior, Performance Settings, and AI Agent Configuration in the SettingsEditor.
- Implemented UI elements for theme selection and management, including current theme display and available themes grid.
- Introduced editor behavior settings such as auto-save options and recent files limit.
- Added performance settings for graphics and memory management.
- Updated keyboard shortcuts section with a placeholder for future customization features.

src/app/editor/system/settings_editor.h

@@ -234,6 +234,10 @@ class SettingsEditor : public Editor {
   Rom* rom_;
   void DrawGeneralSettings();
   void DrawKeyboardShortcuts();
+  void DrawThemeSettings();
+  void DrawEditorBehavior();
+  void DrawPerformanceSettings();
+  void DrawAIAgentSettings();
 };
 
 }  // namespace editor