perf(frontend): 递归组件 Memo 优化 — React.memo + useMemo

TaskTreeViewer:
- Modal/ReceiveConfirmModal/RejectModal/TransferModal 加 React.memo
- TaskNodeCard 递归组件加 React.memo，阻断父节点状态变更引发的整树重渲染
- countAllTasks 用 useMemo 缓存，仅在 task_tree 引用变化时重新计算

TaskListCard:
- TaskNode 递归组件加 React.memo
- countAll 用 useMemo 缓存

frontend/src/components/TaskTree/TaskTreeViewer.tsx

@@ -1,4 +1,4 @@
-import { useState, useCallback } from "react";
+import { useState, useCallback, useMemo, memo } from "react";
 import {
   Search,
   Loader2,
@@ -75,7 +75,7 @@ function getStatusConfig(status: string) {
 // 通用 Modal 容器
 // ============================================================
 
-function Modal({
+const Modal = memo(function Modal({
   open,
   onClose,
   title,
@@ -110,13 +110,13 @@ function Modal({
       </div>
     </div>
   );
-}
+});
 
 // ============================================================
 // 确认接收弹窗
 // ============================================================
 
-function ReceiveConfirmModal({
+const ReceiveConfirmModal = memo(function ReceiveConfirmModal({
   open,
   task,
   submitting,
@@ -163,13 +163,13 @@ function ReceiveConfirmModal({
       </div>
     </Modal>
   );
-}
+});
 
 // ============================================================
 // 品质驳回弹窗
 // ============================================================
 
-function RejectModal({
+const RejectModal = memo(function RejectModal({
   open,
   task,
   submitting,
@@ -244,13 +244,13 @@ function RejectModal({
       </form>
     </Modal>
   );
-}
+});
 
 // ============================================================
 // 完工裂变转交弹窗
 // ============================================================
 
-function TransferModal({
+const TransferModal = memo(function TransferModal({
   open,
   task,
   submitting,
@@ -496,7 +496,7 @@ function TransferModal({
       </form>
     </Modal>
   );
-}
+});
 
 // ============================================================
 // 单个任务节点卡片
@@ -507,7 +507,7 @@ interface ModalTarget {
   action: "receive" | "reject" | "transfer";
 }
 
-function TaskNodeCard({
+const TaskNodeCard = memo(function TaskNodeCard({
   task,
   isLast,
   onAction,
@@ -653,7 +653,7 @@ function TaskNodeCard({
       )}
     </div>
   );
-}
+});
 
 // ============================================================
 // 主容器组件
@@ -779,6 +779,12 @@ export default function TaskTreeViewer() {
 
   // ---- 渲染 ----
 
+  // 🚀 缓存递归计算 — 仅在 task_tree 变化时重新计算
+  const totalTaskCount = useMemo(
+    () => (product?.task_tree ? countAllTasks(product.task_tree) : 0),
+    [product?.task_tree],
+  );
+
   const modalTask = modalTarget?.task ?? null;
 
   return (
@@ -880,7 +886,7 @@ export default function TaskTreeViewer() {
               <p className="text-sm font-semibold text-gray-800">
                 {product.top_level_tasks?.length ?? 0} 顶层
                 {product.task_tree?.length
-                  ? ` · ${countAllTasks(product.task_tree)} 总计`
+                  ? ` · ${totalTaskCount} 总计`
                   : ""}
               </p>
             </div>

frontend/src/components/scan/TaskListCard.tsx

@@ -1,4 +1,5 @@
 /** 任务进度列表卡片 — 递归渲染 task_tree */
+import { useMemo, memo } from "react";
 import { ClipboardList, GitBranch, AlertTriangle } from "lucide-react";
 import type { TaskResponse, TaskSummary } from "../../types/api";
 import { TASK_STATUS } from "../../types/api";
@@ -30,7 +31,7 @@ interface TaskNodeProps {
   depth: number;
 }
 
-function TaskNode({ task, depth }: TaskNodeProps) {
+const TaskNode = memo(function TaskNode({ task, depth }: TaskNodeProps) {
   return (
     <>
       <div className="flex items-center gap-3 px-4 py-3 border-t border-gray-50" style={{ paddingLeft: 16 + depth * 16 }}>
@@ -62,19 +63,22 @@ function TaskNode({ task, depth }: TaskNodeProps) {
       ))}
     </>
   );
-}
+});
 
 function countAll(tasks: TaskResponse[]): number {
   return tasks.reduce((s, t) => s + 1 + (t.child_tasks ? countAll(t.child_tasks) : 0), 0);
 }
 
 export default function TaskListCard({ tasks }: TaskListCardProps) {
+  // 🚀 缓存递归计算
+  const totalCount = useMemo(() => countAll(tasks), [tasks]);
+
   return (
     <div className="rounded-xl bg-white shadow-sm">
       <div className="flex items-center gap-2 border-b border-gray-100 px-4 py-3">
         <ClipboardList className="h-5 w-5 text-blue-600" />
         <h3 className="font-semibold text-gray-800">任务流转树</h3>
-        <span className="ml-auto text-xs text-gray-400">{countAll(tasks)} 个任务</span>
+        <span className="ml-auto text-xs text-gray-400">{totalCount} 个任务</span>
       </div>
       {tasks.length === 0 ? (
         <div className="px-4 py-8 text-center text-sm text-gray-400">暂无关联任务</div>