fix(purchase): 修复 Copy 图标不存在导致的模块加载错误

@element-plus/icons-vue 没有 Copy 图标，改为 CopyDocument

inventory-web/src/views/purchase/index.vue

@@ -80,7 +80,7 @@
             <span>物料明细（{{ formItems.length }} 项）</span>
             <el-button type="primary" plain size="small" :icon="Plus" style="margin-left: 12px;" @click="addFormItem">添加一行</el-button>
             <el-tooltip content="把第一行备注复制到所有行" placement="top">
-              <el-button type="warning" plain size="small" :icon="Copy" style="margin-left: 8px;" @click="syncRemarkToAll">备注同步所有</el-button>
+              <el-button type="warning" plain size="small" :icon="CopyDocument" style="margin-left: 8px;" @click="syncRemarkToAll">备注同步所有</el-button>
             </el-tooltip>
           </div>
 
@@ -276,7 +276,7 @@
 <script setup lang="ts">
 import { ref, computed, onMounted } from 'vue'
 import { useRoute } from 'vue-router'
-import { Refresh, Plus, Delete, Copy } from '@element-plus/icons-vue'
+import { Refresh, Plus, Delete, CopyDocument } from '@element-plus/icons-vue'
 import { ElMessage, ElMessageBox } from 'element-plus'
 import { useUserStore } from '@/stores/user'
 import { searchMaterialPurchase } from '@/api/purchase'