Use POST method for creating new files and PUT for updates.
Gitea requires this distinction - PUT with no SHA fails for new files.
Changes:
- Use POST for creating new files in catalog_push_gitea()
- Use PUT only when existing SHA is available (updates)
- Add explicit branch parameter for consistency
- Bump version to 0.6.0-r2
Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>