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/vehicles/vin-cache-keys.ts

@@ -13,7 +13,7 @@
  * Both the decode path (VehiclesService) and the admin cache-buster
  * (InternalVehiclesService) MUST build keys through here so they stay in sync.
  */
-export const DECODE_CHAIN_VERSION = "2";
+export const DECODE_CHAIN_VERSION = "3";
 
 export function vinResolveCacheKeys(vin: string): {
   cacheKey: string;