1.0.0

feat: add Windows build target + GitHub Actions release CI

- electron-builder configured for Windows NSIS x64
- icon.ico generated for Windows installer
- GitHub Actions workflow builds macOS DMG (arm64) + Windows NSIS on tag push
- Trigger: git tag v* + push

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>