feat(settings): interactive keyboard shortcuts reference section in preferences

[ZhuchkaTriplesix]

Description

Querya Desktop supports more than 25 keyboard shortcuts across SQL editing, tab management, data grid manipulation, connections navigation, and query execution. However, there is no centralized in-app reference.

Proposed Changes

1. Keymap Section:
   • Add a dedicated category or modal in Preferences listing all application keyboard shortcuts.
   • Group by area:
     • SQL Editor: Execute (Ctrl+Enter), Format, Autocomplete, History (Ctrl+H), New Tab (Ctrl+T), Close Tab (Ctrl+W).
     • Data Grid: Copy (Ctrl+C), Copy with Headers (Ctrl+Shift+C), Inspect (Ctrl+I), Set NULL (Alt+N), Duplicate (Ctrl+D), Revert.
     • Navigation: Search Connections (Ctrl+F), Toggle Sidebar, Preferences (Ctrl+,).
2. Interactive Search:
   • Quick search input to filter shortcuts by key combination or description.
3. OS-Aware Badges:
   • Render ⌘ on macOS and Ctrl on Windows/Linux.

[ZhuchkaTriplesix]

Completed and merged into dev via PR #692