feat: filename-aware attachment download endpoint (Content-Disposition), preview download uses it (no popup flash)

app/src/components/common/AttachmentPreview.tsx

@@ -2,6 +2,7 @@ import { useEffect, useState } from 'react';
 import { Download, Loader2 } from 'lucide-react';
 import { Button, Dialog, useToast } from '@/components/ui';
 import { readFull } from '@/lib/att-cache';
+import { attachmentDownload } from '@/lib/api';
 import type { Attachment } from '@/lib/types';
 
 export type AttKind = 'image' | 'pdf' | 'text' | 'audio' | 'video' | 'docx' | 'xlsx' | 'other';
@@ -23,14 +24,6 @@ function b64ToUint8(dataB64: string): Uint8Array<ArrayBuffer> {
   return Uint8Array.from(atob(dataB64), c => c.charCodeAt(0)) as Uint8Array<ArrayBuffer>;
 }
 
-function forceDownload(fileName: string, mime: string | undefined | null, dataB64: string) {
-  const url = URL.createObjectURL(new Blob([b64ToUint8(dataB64)], { type: mime || 'application/octet-stream' }));
-  const a = document.createElement('a');
-  a.href = url;
-  a.download = fileName;
-  a.click();
-  setTimeout(() => URL.revokeObjectURL(url), 60_000);
-}
 
 const KIND_LABEL: Record<AttKind, string> = {
   image: '图片', pdf: 'PDF 文档', text: '文本文件', audio: '音频', video: '视频',
@@ -109,22 +102,17 @@ export function AttachmentPreview({ att, onClose }: { att: Attachment | null; on
       footer={att ? (
         <>
           <Button variant="secondary" className="mr-auto" onClick={() => {
-            // 远程附件：同步新标签打开（用户手势内触发，不会被拦截；右键即可另存）
-            if (att.remote_url) {
-              const a = document.createElement('a');
-              a.href = att.remote_url;
-              a.target = '_blank';
-              a.rel = 'noopener';
-              a.click();
-              toast('success', '已在新的标签页打开，右键图片可「另存为」');
-              return;
-            }
-            // 本地附件：base64 下载，失败给出提示
+            // 统一走服务器下载端点：Content-Disposition 带原始文件名，浏览器直接落盘，不闪窗
             void (async () => {
               try {
-                toast('success', '已开始下载');
-                const r = await readFull(att);
-                forceDownload(att.file_name, att.mime ?? undefined, r.data_b64);
+                const { blob, file_name } = await attachmentDownload(att.id);
+                const url = URL.createObjectURL(blob);
+                const a = document.createElement('a');
+                a.href = url;
+                a.download = file_name;
+                a.click();
+                setTimeout(() => URL.revokeObjectURL(url), 60_000);
+                toast('success', '已下载：' + file_name);
               } catch (e) {
                 toast('error', '下载失败：' + (e as Error).message);
               }