feat(sync): gate CUI invalid/ANAF-notFound → ERROR inainte de import Oracle

Incident 22.04.2026 (#485225171 NONA ROYAL SRL): clientul a inversat
cod_fiscal cu registru in GoMag → sistem a creat partener cu CUI=J1994000194225.

Adauga evaluate_cui_gate() care blocheaza comanda (ERROR) daca:
- CUI format invalid (ex: J.. in loc de cifre)
- CUI nu trece cifra de control
- ANAF returneaza explicit notFound (scpTVA=None + denumire_anaf="")

ANAF down (anaf_data=None) → fallback pass, comportament existent pastrat.
_record_order_error() DRY helper evita duplicarea upsert/add_items.
Contract ANAF down/notFound/found documentat in anaf_service._call_anaf_api.
9 teste unit (inclusiv T5 CRITIC: ANAF down nu blocheaza) + T7 COALESCE.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

api/app/services/anaf_service.py

@@ -141,6 +141,12 @@ async def _call_anaf_api(body: list[dict], retry: int = 0, log_fn=None) -> dict[
 
             checked_at = datetime.now().isoformat()
 
+            # CONTRACT (consumed by sync_service.evaluate_cui_gate):
+            #   Return {}                                       → transient error (down/429/5xx/timeout)
+            #   Return {cui: {scpTVA: None, denumire_anaf: ""}} → ANAF notFound explicit
+            #   Return {cui: {scpTVA: bool, denumire_anaf: str}} → ANAF found
+            # If you change this semantics, update the gate in sync_service too.
+
             # Parse ANAF response
             found_list = data.get("found", [])
             for item in found_list: