Resolve all security vulnerabilities, bug fixes, and print watermarking configurations based on product review

refactor: safe editor folding, centralize api client headers, sync cloud preferences, and add tests

feat: make realtime AI tools hideable, add layout toggle, and ensure dropdowns are fully theme aware

fix: restore menu button toggle on desktop, optimize mobile button responsiveness, and sync landing page preview styling

feat: add close buttons to Folder Sidebar, Sync Logs, AI Panel, and Live Preview

fix: resolve overflowing header controls and layout responsiveness in editor & main toolbar

refactor: Modularize frontend App.tsx into custom hooks and components and resolve Vite import.meta types