fix(decode): recognize VXK WMI as Opel (PSA/Stellantis-platform Corsa F, Mokka B)

Customer entered VXKUPHNKSP4032040 (2023 Corsa F) and got a bare
'Marka desteklenmiyor' — VXK was missing from all three WMI maps, so
identifyBasic could not even name the brand. PL24's opel_parts catalog
ends at CORSA-E (2015-2019, verified via the model-picker page), so the
catalog itself stays a gap, but the user now gets the honest
'Opel 2023 olarak tanındı, katalog henüz mevcut değil' message and the
miss is logged for the coverage backlog.

- WMI_BRAND_MAP + PL24_WMI_SERVICE_MAP + EMEX CATALOG_MAP: VXK -> Opel
- DECODE_CHAIN_VERSION 2 -> 3 (brand-mapping change; invalidates the
  stale negative cache for the customer's VIN)
- vin-cache-keys.spec: lock-key assertion checked the bare version char,
  which now appears inside the test VIN — assert the ✌️ segment instead

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

apps/api/src/integrations/pl24/pl24.types.ts

@@ -565,6 +565,7 @@ export const PL24_WMI_SERVICE_MAP: Record<string, string> = {
   // Opel / Vauxhall
   W0L: "opel_parts", // Opel AG (Germany)
   W0V: "opel_parts", // Opel (newer Stellantis-era WMI)
+  VXK: "opel_parts", // PSA/Stellantis-platform Opel (Corsa F, Mokka B — France/Spain plants)
 
   // Citroën (PSA)
   VF7: "citroen_parts", // Citroën SA (France)