feat: 优化追问功能 - LLM智能生成 + 显示位置修复

- 修复 AuthLoader 组件中 router.push 在渲染期间调用的 React 警告
- 追问问题改为只在最新 AI 回复下方显示（修复多处显示问题）
- 新增 LLM 生成追问 API：POST /api/v1/apps/{id}/suggestions
- 前端调用 LLM API 生成智能追问，失败时降级到规则生成
- 登录页填入默认测试账号 kj-admin@govai.gov.cn

apps/web/src/components/app-ui/agent-ui.tsx

@@ -140,6 +140,7 @@ interface AgentUIProps {
 export default function AgentUI({ app }: AgentUIProps) {
   const router = useRouter();
   const queryClient = useQueryClient();
+  const [conversationId, setConversationId] = useState<string | undefined>();
   const [messages, setMessages] = useState<Message[]>(
     app.welcome_message && !conversationId
       ? [{ id: "welcome", role: "assistant", content: app.welcome_message }]
@@ -147,7 +148,6 @@ export default function AgentUI({ app }: AgentUIProps) {
   );
   const [input, setInput] = useState("");
   const [isStreaming, setIsStreaming] = useState(false);
-  const [conversationId, setConversationId] = useState<string | undefined>();
   const [selectMode, setSelectMode] = useState(false);
   const [selectedIds, setSelectedIds] = useState<Set<string>>(new Set());
   const [deleteTarget, setDeleteTarget] = useState<{