feat(bloco-c): motor fiscal com legal_basis obrigatorio, classificacao NCM, seguranca CEST/IPI e validador GTIN

central/app/enrichment/kb.py

@@ -72,6 +72,11 @@ def name_candidates(session, description) -> list[KbProduct]:
 
 
 def upsert_product(session, key: str | None, description, *, brand=None, quantity=None) -> KbProduct:
+    if key:
+        from ..gtin_validator import validate_gtin
+        valid, _ = validate_gtin(key)
+        if not valid:
+            key = None  # Regra C.6: GTIN inválido (DV ou prefixo errado) não entra na KB
     product = find_by_gtin(session, key)
     if product is None:
         fp = gtin_fingerprint(key) if key else hashlib.sha256(f"name:{textnorm.fingerprint(description)}".encode()).hexdigest()