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/emex/emex.types.ts

@@ -348,6 +348,7 @@ export const CATALOG_MAP: Record<string, CatalogEntry> = {
   // Opel
   W0L: { code: "GM_OP201809", brand: "Opel" },
   W0V: { code: "GM_OP201809", brand: "Opel" }, // newer Stellantis-era WMI
+  VXK: { code: "GM_OP201809", brand: "Opel" }, // PSA/Stellantis-platform Opel (Corsa F, Mokka B)
   // Chevrolet
   KL1: { code: "GM_C201809", brand: "Chevrolet" },
   // SsangYong