fix: 更正 CloudCost API 默认地址为后端 Container App

前端 Static Web App 地址无 API，改为正确的后端地址。

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

langgraph/src/agent/utils/config.ts

@@ -127,6 +127,6 @@ export const config = {
     fallbackEndpoint: process.env.DOC_CREATOR_FALLBACK_ENDPOINT ?? "",
   },
   cloudcost: {
-    apiBase: process.env.CLOUDCOST_API_BASE ?? "https://orange-wave-09002e800.7.azurestaticapps.net",
+    apiBase: process.env.CLOUDCOST_API_BASE ?? "https://cloudcost-brank.yellowground-bf760827.southeastasia.azurecontainerapps.io",
   },
 } as const;