fix: LangGraph管理页全屏布局 + 健康检查修复

- LangGraphAdmin.vue: flex全屏布局，表格自适应高度
- monitoring.py: Java后端检查由GET /api/改为POST /api/admin-auth/login-by-password
- monitoring.py: LLM检查由ainvoke改为abatch(max_tokens=1)加速
- .env.production: JAVA_BASE_URL改为172.17.0.1(Docker桥接网关)

cfc-langgraph/app/monitoring.py

@@ -124,7 +124,7 @@ async def detailed_health():
         from app.tools.java_client import JavaClient
         client = JavaClient()
         jc = await client._get_client()
-        resp = await jc.get("/api/")
+        resp = await jc.post("/api/admin-auth/login-by-password", json={})
         if resp.status_code == 401:
             status["components"]["java_backend"] = {"status": "ok", "detail": "需认证（正常）"}
         elif resp.status_code == 200: