Update config defs

backend/src/core/config/config-loader.ts

@@ -41,13 +41,13 @@ const configSchema = z.object({
     audience: z.string(),
   }),
 
-  // External APIs configuration
+  // External APIs configuration (optional)
   external: z.object({
     vpic: z.object({
       url: z.string(),
       timeout: z.string(),
-    }),
-  }),
+    }).optional(),
+  }).optional(),
 
   // Service configuration
   service: z.object({