feat: add per-project settings gear button and compact context menu (#159)

- Add Settings gear button on each project item (appears on hover)
- Click gear navigates to Project Settings page with correct project selected
- Add 'Settings' item to right-click context menu
- Remove Settings button from TitleBar (top right)
- Remove Ctrl+N shortcut labels from project items
- Compact context menu styling (smaller padding, font, icons)
- Rename 'Set Default Shell' to 'Default Shell' in context menu