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/schemas/ocr.py

@@ -60,6 +60,8 @@ class ExtractionData(BaseModel):
     confidence_date: float = Field(default=0.0, ge=0, le=1, description="Date extraction confidence")
     confidence_vendor: float = Field(default=0.0, ge=0, le=1, description="Vendor extraction confidence")
     confidence_client: float = Field(default=0.0, ge=0, le=1, description="Client extraction confidence")
+    confidence_tva: float = Field(default=0.0, ge=0, le=1, description="TVA extraction confidence")
+    confidence_payment: float = Field(default=0.0, ge=0, le=1, description="Payment extraction confidence")
     overall_confidence: float = Field(default=0.0, ge=0, le=1, description="Overall confidence score")
     raw_text: str = Field(default="", description="Raw OCR text (primary)")
     raw_texts: List[str] = Field(default=[], description="Raw OCR texts from all engine passes (for analysis)")