- Add timestamped backup at `~/.cc-switch/config.v1.backup.<ts>.json`
- Keep provider files untouched; only cc-switch metadata is backed up
- Remove UI notification plan; backup only as requested
- Update CHANGELOG with migration backup notes
- Add typecheck script for TypeScript validation
- Add format and format:check scripts for code formatting
- Create comprehensive CHANGELOG documenting migration from Electron to Tauri
- Document all major changes, improvements, and migration notes for v3.0.0