feat(images): default frontend assets to image service

app/gateway-frontend/src/env.d.ts

@@ -11,6 +11,8 @@ interface ImportMetaEnv {
     readonly VITE_GATEWAY_API_URL?: string;
     readonly VITE_GAME_API_URL_TEMPLATE?: string;
     readonly VITE_GAME_ASSET_URL?: string;
+    readonly VITE_IMAGE_PUBLIC_URL?: string;
+    readonly VITE_GATEWAY_USER_ICON_BASE_URL?: string;
     readonly VITE_GAME_WEB_URL?: string;
     readonly VITE_GAME_WEB_URL_TEMPLATE?: string;
 }