Implement welcome screen and enhance session management in EditorManager

- Added a welcome screen that can be accessed from the View menu, improving user experience for new users.
- Enhanced session management by allowing the reuse of empty sessions when loading ROMs, reducing unnecessary session creation.
- Improved the session table layout for better readability and added a custom overworld feature flag for each session.
- Updated the DrawWelcomeScreen method for better visual integration and added a glow effect to the decorative line.

src/app/editor/system/settings_editor.h

@@ -228,6 +228,8 @@ class SettingsEditor : public Editor {
   // Get the ROM pointer
   Rom* rom() const { return rom_; }
 
+  bool IsRomLoaded() const override { return true; } // Allow access without ROM for global settings
+
  private:
   Rom* rom_;
   void DrawGeneralSettings();