fix(settings): add fault-tolerant default accessors for robust settings handling (#337)

- Added safeExplorerSettings(), safeFilesSettings(), safeThemeSettings() helper functions
- These helpers provide fallback to DEFAULT_SETTINGS when settings are corrupted or undefined
- Prevents 'Cannot read properties of undefined' errors in SettingsDialog
- Imported DEFAULT_SETTINGS from SettingsContext for robust fallback defaults
- Updated explorer sortOrder, files confirmDragAndDrop, and theme settings accessors
- Ensures GUI remains functional even if config files are corrupted or missing

AGENT5: Settings Components fault tolerance fix

Co-authored-by: Droid Agent <droid@factory.ai>

Author: echobt