📚 Update README: Document intelligent change detection system

🆕 COMPREHENSIVE DOCUMENTATION UPDATE

## New Content Added:
### Intelligent Change Detection System
- Documents YAML hash monitoring and remote repository tracking
- Explains performance optimization (seconds vs minutes)
- Details the new selective rebuild logic

### Updated Workflow Documentation
- Enhanced Mermaid sequence diagram with change detection flow
- Updated make targets with new utility commands
- Added force-build options and cache management

### Technical Implementation Details
- Documents check_changes.sh script functionality
- Explains cache system (.cache/ directory)
- Details GitHub API integration for remote monitoring

### Repository Mapping Documentation
- digitalesysteme → VL_EingebetteteSysteme
- prozprog → VL_ProzeduraleProgrammierung
- softwareentwicklung → VL_Softwareentwicklung
- robotikprojekt → VL_Robotikprojekt

### Troubleshooting Section
- Common scenarios and solutions
- Performance metrics and expectations
- Remote repository update handling

### Updated File Structure
- Documents new files: check_changes.sh, .cache/, .gitignore
- Shows current PDF naming examples
- Reflects improved Makefile capabilities

## Key Improvements:
✅ Comprehensive coverage of all new features
✅ Clear performance expectations documented
✅ Troubleshooting guide for common issues
✅ Technical details for maintenance and debugging
✅ Updated workflow diagrams and examples

The README now fully reflects the production-ready intelligent
build system with remote repository monitoring capabilities.

Author: SebastianZug