feat(admin-web): 批量下载增加进度条显示

- 显示打包进度和下载进度两个阶段
- 进度条实时更新百分比
- 使用 File System Access API 支持用户选择保存位置

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

frontend/admin-web/src/app/(dashboard)/contracts/contracts.module.scss

@@ -172,4 +172,40 @@
   &__statusGray {
     color: #4b5563 !important;
   }
+
+  // 进度条样式
+  &__progressContainer {
+    background: var(--bg-secondary, #f8f9fa);
+    border-radius: 8px;
+    padding: 1rem 1.5rem;
+    display: flex;
+    flex-direction: column;
+    gap: 0.5rem;
+  }
+
+  &__progressLabel {
+    font-size: 0.875rem;
+    color: var(--text-primary, #212529);
+    font-weight: 500;
+  }
+
+  &__progressBar {
+    height: 12px;
+    background: var(--border-color, #dee2e6);
+    border-radius: 6px;
+    overflow: hidden;
+  }
+
+  &__progressFill {
+    height: 100%;
+    background: linear-gradient(90deg, #0d6efd, #0dcaf0);
+    border-radius: 6px;
+    transition: width 0.3s ease;
+  }
+
+  &__progressText {
+    font-size: 0.875rem;
+    color: var(--text-secondary, #6c757d);
+    text-align: right;
+  }
 }

frontend/admin-web/src/app/(dashboard)/contracts/page.tsx

@@ -142,6 +142,8 @@ export default function ContractsPage() {
   // 批量下载状态
   const [batchDownloading, setBatchDownloading] = useState(false);
   const [batchProgress, setBatchProgress] = useState(0);
+  const [downloadStage, setDownloadStage] = useState<'idle' | 'packaging' | 'downloading'>('idle');
+  const [downloadProgress, setDownloadProgress] = useState(0);
 
   // 轮询任务状态直到完成
   const pollTaskUntilComplete = async (taskNo: string): Promise<string | null> => {
@@ -172,11 +174,7 @@ export default function ContractsPage() {
     try {
       // 检查浏览器是否支持 File System Access API
       if ('showSaveFilePicker' in window) {
-        // 先下载文件内容
-        const response = await fetch(url);
-        const blob = await response.blob();
-
-        // 弹出保存对话框让用户选择位置
+        // 弹出保存对话框让用户选择位置（先选择再下载）
         const fileHandle = await (window as unknown as { showSaveFilePicker: (options: unknown) => Promise<FileSystemFileHandle> }).showSaveFilePicker({
           suggestedName,
           types: [{
@@ -185,11 +183,44 @@ export default function ContractsPage() {
           }],
         });
 
+        // 用户选择了保存位置后，开始下载并显示进度
+        setDownloadStage('downloading');
+        setDownloadProgress(0);
+
+        const response = await fetch(url);
+        const contentLength = response.headers.get('content-length');
+        const total = contentLength ? parseInt(contentLength, 10) : 0;
+
+        if (!response.body) {
+          throw new Error('无法读取响应流');
+        }
+
+        const reader = response.body.getReader();
+        const chunks: Uint8Array[] = [];
+        let loaded = 0;
+
+        while (true) {
+          const { done, value } = await reader.read();
+          if (done) break;
+
+          chunks.push(value);
+          loaded += value.length;
+
+          if (total > 0) {
+            const progress = Math.round((loaded / total) * 100);
+            setDownloadProgress(progress);
+          }
+        }
+
+        // 合并所有 chunks 为 Blob
+        const blob = new Blob(chunks);
+
         // 写入文件
         const writable = await fileHandle.createWritable();
         await writable.write(blob);
         await writable.close();
 
+        setDownloadProgress(100);
         return true;
       }
     } catch (error) {
@@ -203,6 +234,8 @@ export default function ContractsPage() {
   const handleBatchDownload = async () => {
     setBatchDownloading(true);
     setBatchProgress(0);
+    setDownloadStage('packaging');
+    setDownloadProgress(0);
 
     try {
       toast.info('正在准备批量下载，请稍候...');
@@ -252,6 +285,8 @@ export default function ContractsPage() {
     } finally {
       setBatchDownloading(false);
       setBatchProgress(0);
+      setDownloadStage('idle');
+      setDownloadProgress(0);
     }
   };
 
@@ -264,6 +299,8 @@ export default function ContractsPage() {
 
     setBatchDownloading(true);
     setBatchProgress(0);
+    setDownloadStage('packaging');
+    setDownloadProgress(0);
 
     try {
       toast.info('正在准备增量下载，请稍候...');
@@ -312,6 +349,8 @@ export default function ContractsPage() {
     } finally {
       setBatchDownloading(false);
       setBatchProgress(0);
+      setDownloadStage('idle');
+      setDownloadProgress(0);
     }
   };
 
@@ -420,7 +459,11 @@ export default function ContractsPage() {
 
           <div className={styles.contracts__actions}>
             <Button variant="primary" onClick={handleBatchDownload} disabled={batchDownloading}>
-              {batchDownloading ? `打包中 ${batchProgress}%...` : '批量下载 ZIP'}
+              {batchDownloading
+                ? downloadStage === 'packaging'
+                  ? `打包中 ${batchProgress}%`
+                  : `下载中 ${downloadProgress}%`
+                : '批量下载 ZIP'}
             </Button>
             {lastDownloadTime && (
               <Button variant="outline" onClick={handleIncrementalDownload} disabled={batchDownloading}>
@@ -430,6 +473,24 @@ export default function ContractsPage() {
           </div>
         </div>
 
+        {/* 下载进度条 */}
+        {batchDownloading && (
+          <div className={styles.contracts__progressContainer}>
+            <div className={styles.contracts__progressLabel}>
+              {downloadStage === 'packaging' ? '正在打包合同文件...' : '正在下载到本地...'}
+            </div>
+            <div className={styles.contracts__progressBar}>
+              <div
+                className={styles.contracts__progressFill}
+                style={{ width: `${downloadStage === 'packaging' ? batchProgress : downloadProgress}%` }}
+              />
+            </div>
+            <div className={styles.contracts__progressText}>
+              {downloadStage === 'packaging' ? batchProgress : downloadProgress}%
+            </div>
+          </div>
+        )}
+
         {/* 合同列表 */}
         <div className={styles.contracts__table}>
           <div className={styles.contracts__tableHeader}>