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>

README.md

@@ -64,6 +64,9 @@ chmod +x CloudronPackagingWorkspace/*.sh
 
 ### 2. Create Feature Branch
 ```bash
+# Start from integration branch (not main!)
+git checkout integration
+git pull origin integration
 git checkout -b feature/package-[appname]
 ```
 
@@ -119,7 +122,7 @@ git push origin feature/package-[appname]
 ## 🏷️ Git Workflow
 
 ### Branch Strategy
-- **`master`**: Stable, production-ready packages
+- **`main`**: Stable, production-ready packages
 - **`integration`**: Integration branch for testing multiple packages
 - **`feature/package-[appname]`**: Individual application packaging
 - **`hotfix/[appname]-[issue]`**: Critical fixes