feat(data-entry): Add unified receipt form with OCR confidence tracking

New unified receipt creation system with:
- UnifiedReceiptForm component with inline OCR preview and confidence indicators
- Compact upload zone with drag-drop and camera support
- TVA and Payment fields with dynamic add/remove
- Supplier dual-field with autocomplete and OCR hint
- Receipt form sections with collapsible auxiliary data

Backend OCR improvements:
- Add confidence_tva and confidence_payment to extraction results
- Update TVA extraction to return confidence scores
- Include TVA (15%) and payment (10%) in overall_confidence calculation

Also includes:
- CSS design system rules documentation
- Port check helper function for service scripts
- Expanded design tokens documentation in CLAUDE.md

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

backend/modules/data_entry/routers/ocr.py

@@ -618,6 +618,8 @@ def _dict_to_extraction_data(data: dict) -> ExtractionData:
         confidence_date=data.get('confidence_date', 0.0),
         confidence_vendor=data.get('confidence_vendor', 0.0),
         confidence_client=data.get('confidence_client', 0.0),
+        confidence_tva=data.get('confidence_tva', 0.0),
+        confidence_payment=data.get('confidence_payment', 0.0),
         overall_confidence=data.get('overall_confidence', 0.0),
         raw_text=data.get('raw_text', ''),
         raw_texts=data.get('raw_texts', []),