Optimize workflow: Local generation with intelligent GitHub Action

🚀 Major workflow improvements:

## GitHub Action Optimization
- Simplified from heavy cloud generation to lightweight deployment
- Intelligent detection of changed YAML files via git diff
- Conditional regeneration only when needed (changed YAML or missing HTML)
- Fixed syntax error in PDF counting loop (2>/dev/null redirect)
- Dramatic reduction in GitHub Actions minutes usage

## Documentation Enhancement
- Added comprehensive README with Mermaid sequence diagram
- Documented complete workflow from local development to deployment
- Clear explanation of hybrid approach benefits
- Usage examples for all make targets

## Technical Details
- Hybrid approach: Local development + intelligent cloud fallback
- Course-specific asset organization maintained
- Automatic path correction for PDF references
- DRY principle implementation in Makefile

This creates an efficient development workflow:
1. Fast local development with immediate feedback
2. Automated asset organization and git integration
3. Intelligent cloud deployment as safety net
4. Comprehensive documentation for team collaboration

Author: SebastianZug

.github/workflows/generateOERoverview.yml

@@ -111,13 +111,13 @@ jobs:
           find assets/ -type d 2>/dev/null || echo "No asset directories"
           echo ""
           echo "PDF counts per course:"
-          for dir in assets/*/pdf 2>/dev/null; do
-            if [ -d "$dir" ]; then
+          for dir in assets/*/pdf; do
+            if [ -d "$dir" ] 2>/dev/null; then
               course=$(basename $(dirname "$dir"))
               count=$(ls -1 "$dir"/*.pdf 2>/dev/null | wc -l)
               echo "  $course: $count PDFs"
             fi
-          done
+          done 2>/dev/null || echo "  No PDF directories found"
           
           echo ""
           echo "Generated in this run:"