feat: add cross-platform release pipeline and app icons
- Update tauri.conf.json with multi-platform bundle config (macOS unsigned, Windows unsigned)
- Add app icon (1024x1024 source) and generate all required sizes (png, icns, ico)
- Add generate-icons.sh script for regenerating icons from source PNG
- Add GitHub Actions release workflow for 4-target parallel builds (macOS ARM/x64, Linux, Windows)
- Simplify release.sh with tag-based publish instructions
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via [Happy](https://happy.engineering)
Co-Authored-By: Claude <noreply@anthropic.com>
Co-Authored-By: Happy <yesreply@happy.engineering>
9717a64310