feat(ocr): Add validation system and CLIENT CUI extraction

OCR Data Extraction Validation System:
- Add 7 validation rules (amount range, TVA ratio, payment sum, etc.)
- Add Medium preprocessing to replace Heavy (fixes digit concatenation)
- Add validation warnings to API responses
- Flag receipts needing manual review (needs_manual_review field)
- Add database migration for needs_manual_review column

CLIENT CUI Extraction Improvements:
- Support all format variations: CIF CLIENT:, CLIENT C.U.I/C.I.F., etc.
- Handle OCR errors (R0 vs RO, C1F vs CIF)
- Add client_name, client_cui, client_address to API response
- Add validation fields to API response (was missing)

QA Review: 12 issues found, 9 fixed (5 errors + 4 warnings)
- Fixed type safety in validation rules
- Fixed ZeroDivisionError risk
- Fixed schema mismatch (Optional[bool] for needs_manual_review)
- All 37 unit tests passing

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

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

backend/modules/data_entry/schemas/ocr.py

@@ -20,6 +20,15 @@ class PaymentMethod(BaseModel):
     amount: Decimal = Field(description="Amount paid")
 
 
+class ValidationWarning(BaseModel):
+    """Validation warning from OCR extraction."""
+    field: str = Field(description="Field name (e.g., 'amount', 'tva_total')")
+    rule: str = Field(description="Rule name (e.g., 'amount_range', 'tva_ratio')")
+    message: str = Field(description="Human-readable warning message")
+    severity: str = Field(description="Severity: 'info', 'warning', 'error'")
+    suggested_value: Optional[str] = Field(default=None, description="Suggested corrected value")
+
+
 class ExtractionData(BaseModel):
     """Extracted receipt data from OCR."""
 
@@ -56,6 +65,13 @@ class ExtractionData(BaseModel):
     ocr_engine: str = Field(default="", description="OCR engine used: paddleocr or tesseract")
     processing_time_ms: int = Field(default=0, ge=0, description="Processing time in milliseconds")
 
+    # Validation results (added by bon-ocr-validation feature)
+    # needs_manual_review: None = not validated yet (old receipts), False = no review needed, True = needs review
+    needs_manual_review: Optional[bool] = Field(default=None, description="Flag for supervisor review (None=not validated, False=ok, True=needs review)")
+    validation_warnings: List[str] = Field(default=[], description="Validation warnings")
+    validation_errors: List[str] = Field(default=[], description="Validation errors")
+    inter_ocr_ratios: dict[str, float] = Field(default={}, description="Inter-OCR consistency ratios")
+
     class Config:
         """Pydantic config."""
         json_schema_extra = {