feat: add task workflow and asset downloads

components/asset-manager.tsx

@@ -1,7 +1,7 @@
 "use client";
 
 import { useEffect, useMemo, useRef, useState } from "react";
-import { Eye, ImageIcon, Info, Loader2, Music, RefreshCw, Trash2, X } from "lucide-react";
+import { Download, Eye, ImageIcon, Info, Loader2, Music, RefreshCw, Trash2, X } from "lucide-react";
 import { clampPage, pageItems, Pagination } from "@/components/pagination";
 import { modalEnter, modalExit, pulseFeedback, revealChildren, runScopedMotion } from "@/lib/ui/motion";
 import type { Asset, GenerationJob } from "@/lib/types";
@@ -208,6 +208,9 @@ export function AssetManager() {
                       <button className="button mini-button" type="button" title="预览" aria-label={`预览 ${asset.name}`} onClick={() => setPreviewAsset(asset)}>
                         <Eye size={15} />
                       </button>
+                      <a className="button mini-button" href={assetDownloadUrl(asset)} title="下载" aria-label={`下载 ${asset.name}`}>
+                        <Download size={15} />
+                      </a>
                       <button className="button danger mini-button" type="button" title="删除" aria-label={`删除 ${asset.name}`} onClick={() => removeAsset(asset)} disabled={deletingAssetId === asset.id}>
                         {deletingAssetId === asset.id ? <Loader2 className="spin" size={15} /> : <Trash2 size={15} />}
                       </button>
@@ -264,9 +267,14 @@ export function AssetManager() {
                 <strong>{previewAsset.name}</strong>
                 <span className="muted compact-hint">{kindLabel(previewAsset)} / {sourceLabel(previewAsset.source)} / {formatDate(previewAsset.createdAt)}</span>
               </div>
-              <button className="icon-button" type="button" title="关闭预览" aria-label="关闭预览" ref={closeButtonRef} onClick={closePreview}>
-                <X size={18} />
-              </button>
+              <div className="asset-preview-actions">
+                <a className="icon-button" href={assetDownloadUrl(previewAsset)} title="下载" aria-label={`下载 ${previewAsset.name}`}>
+                  <Download size={18} />
+                </a>
+                <button className="icon-button" type="button" title="关闭预览" aria-label="关闭预览" ref={closeButtonRef} onClick={closePreview}>
+                  <X size={18} />
+                </button>
+              </div>
             </div>
             <div className="asset-preview-media">
               {renderAssetPreviewLarge(previewAsset)}
@@ -372,6 +380,10 @@ function renderAssetPreviewLarge(asset: Asset) {
   );
 }
 
+function assetDownloadUrl(asset: Asset) {
+  return `/api/assets/${encodeURIComponent(asset.id)}/download`;
+}
+
 function isResultAsset(asset: Asset, outputAssetIds: Set<string>) {
   if (!outputAssetIds.has(asset.id)) return false;
   if (asset.kind === "mask" || asset.tags.includes("mask") || typeof asset.metadata.maskRule === "string") return false;