Add configurable global hotkeys in Settings tab

Users can now customize or disable the Quick Launch (⌃⌥G) and Window
Switcher (⌃⌥P) keyboard shortcuts from a new Hotkeys tab in Settings.
Hotkey configs persist across app restarts via UserDefaults.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

Author: Chris Fields