fix: increase VIN decode timeout to 60s for Gemini cold start (refs #229)

Default 10s API client timeout caused frontend "Failed to decode" errors
when Gemini engine cold-starts (34s+ on first call).

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

frontend/src/features/vehicles/api/vehicles.api.ts

@@ -86,7 +86,9 @@ export const vehiclesApi = {
    * Requires Pro or Enterprise tier
    */
   decodeVin: async (vin: string): Promise<DecodedVehicleData> => {
-    const response = await apiClient.post('/vehicles/decode-vin', { vin });
+    const response = await apiClient.post('/vehicles/decode-vin', { vin }, {
+      timeout: 60000 // 60 seconds for Gemini cold start
+    });
     return response.data;
   }
 };