Shortcuts become data-driven

Droid gains a shortcut reference catalog backed by JSON configuration and supporting UI components.

That makes keyboard behavior easier to document, display, and evolve without turning every shortcut tweak into a treasure hunt.

• Implemented shortcut reference catalog with JSON configuration
• Refined sidebar menus and sidebar UI components
• Updated generated model catalog
• Cleaned README, license, docs, and app visuals
• Refactored code structure for readability and maintainability