Phase 2 of Dolt integration - enables runtime backend selection:
- Add --backend flag to bd init (sqlite|dolt)
- Create storage factory for backend instantiation
- Update daemon and main.go to use factory with config detection
- Update database discovery to find Dolt backends via metadata.json
- Fix Dolt schema init to split statements for MySQL compatibility
- Add ReadOnly mode to skip schema init for read-only commands
Usage: bd init --backend dolt --prefix myproject
Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>