Add complete Gitea package publishing support

✨ Features:
- GiteaPackageRegistry client for PyPI-compatible uploads
- Enhanced release.py with upload/registry commands
- New Makefile targets for Gitea publishing workflow
- Comprehensive documentation with examples

📦 New Commands:
- `release.py registry` - Show registry info & authentication
- `release.py upload` - Upload packages to Gitea
- `release.py publish --to-gitea` - Complete release + upload
- `make release-publish-gitea VERSION=x.y.z` - One-command release

🔧 Infrastructure:
- Automatic package detection (wheel + sdist)
- Dry-run support for safe testing
- Error handling and detailed feedback
- Authentication validation

📚 Documentation:
- PACKAGE_PUBLISHING.md with complete setup guide
- Usage examples and troubleshooting

🚀 Generated with [Claude Code](https://claude.ai/code)

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

gitea/__init__.py

@@ -24,10 +24,12 @@ from .client import GiteaClient
 from .models import Issue, Milestone, Label, ProjectState, Priority
 from .config import GiteaConfig
 from .exceptions import GiteaError, GiteaAuthError, GiteaNotFoundError
+from .package_registry import GiteaPackageRegistry
 
 __all__ = [
     'GiteaClient',
     'Issue', 'Milestone', 'Label', 'ProjectState', 'Priority',
     'GiteaConfig',
-    'GiteaError', 'GiteaAuthError', 'GiteaNotFoundError'
+    'GiteaError', 'GiteaAuthError', 'GiteaNotFoundError',
+    'GiteaPackageRegistry'
 ]