Enhance .gitignore for packaging workflow

- Add patterns for temporary packaging directories
- Include Docker container artifacts exclusion
- Add common OS-generated file patterns
- Maintain existing upstream repo exclusions

This supports the container-based packaging workflow for ~100 Cloudron applications while keeping the repository clean.

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

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

.gitignore

@@ -1,2 +1,19 @@
 CloudronPackagingWorkspace/Docker/*
-CloudronPackagingWorkspace/NonDocker/*
+CloudronPackagingWorkspace/NonDocker/*
+
+# Temporary packaging work directories
+temp_*
+*_package_new/
+packaging_temp/
+
+# Docker container artifacts
+.dockerignore
+
+# OS generated files
+.DS_Store
+.DS_Store?
+._*
+.Spotlight-V100
+.Trashes
+ehthumbs.db
+Thumbs.db