feat(ui): redesign touch key bar with modifier keys and iOS-style layout

- Two-row key bar with Ctrl/Shift modifier toggle buttons
- iOS keyboard-style styling with flash feedback on press
- Escape key, Ctrl+letter combos, Shift+arrow selection support
- Side panel branding with TermBeam logo and version display
- Improved touch handling with swipe-vs-tap detection
- Light/dark theme support for all new key styles

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

Author: dorlugasigal