refactor: migrate from master to main branch + implement PR workflow

- Rename master branch to main for inclusive language
- Update all documentation references from master → main
- Implement PR-based workflow with maintainer approval required
- Document tea CLI usage for Gitea pull requests
- Establish clear branch hierarchy: feature → integration → main

Branch Strategy:
- main: Production packages (requires PR approval)
- integration: Staging area for multiple packages
- feature/package-[name]: Individual package development

Workflow Pattern:
1. Create feature/package-[name] from integration
2. Develop package in feature branch
3. Merge feature → integration (direct merge)
4. Create PR integration → main (requires approval)

This provides proper quality gates while enabling parallel development
of the 56 applications with maintainer oversight.

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

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

CloudronPackages/README.md

@@ -67,7 +67,7 @@ docker logs [container-id]
 2. **Testing**: Build and validate package functionality
 3. **Finalization**: Move completed package to `CloudronPackages/[AppName]/`
 4. **Documentation**: Ensure all required files and build notes are complete
-5. **Git Workflow**: Commit via feature branch → integration → master
+5. **Git Workflow**: Commit via feature branch → integration → main
 
 ### Quality Standards
 All packages in this directory must meet: