feat(orders): 一键导出改为所有分层/分组的 SVG 压缩包（前端 createLayerExportZip 打包）

backend/service/app.py

@@ -1001,7 +1001,7 @@ def get_order(request: Request, order_no: str) -> dict:
 
 @app.get("/api/orders/{order_no}/design")
 def order_design(request: Request, order_no: str) -> dict:
-    """订单设计详情：画布 + 各层元素（含素材 URL），供前端做分层/整体预览。"""
+    """订单设计详情：完整 CanvasDocument + 素材映射，供前端分层/整体预览与分层 SVG 导出。"""
     _require_orders_auth(request)
     path = Path(_order_dir(order_no)) / "order.json"
     if not path.exists():
@@ -1014,19 +1014,21 @@ def order_design(request: Request, order_no: str) -> dict:
     data = json.loads(tjson.read_text(encoding="utf-8"))
     doc = data.get("document") or {}
 
-    elements = []
+    # 素材映射：元素 assetId -> {id,type(source 是 svg 还是 image),source(下载 URL)}
+    assets: dict[str, dict] = {}
     for e in doc.get("elements") or []:
         if not isinstance(e, dict):
             continue
-        item = dict(e)
-        asset_id = e.get("assetId")
-        if asset_id:
-            meta = _read_asset_meta(_asset_dir(str(asset_id))) or {}
-            item["assetUrl"] = meta.get("file_url") or f"/api/assets/{asset_id}/download"
-            item["assetName"] = meta.get("name") or str(asset_id)
-        else:
-            item["assetUrl"] = ""
-        elements.append(item)
+        aid = e.get("assetId")
+        if not aid or str(aid) in assets:
+            continue
+        meta = _read_asset_meta(_asset_dir(str(aid))) or {}
+        mime = str(meta.get("mime_type") or "")
+        assets[str(aid)] = {
+            "id": str(aid),
+            "type": "svg" if mime in ("image/svg+xml",) else "image",
+            "source": meta.get("file_url") or f"/api/assets/{aid}/download",
+        }
 
     try:
         status = manager.get_status(str(o.get("job_id") or "")).status
@@ -1038,13 +1040,15 @@ def order_design(request: Request, order_no: str) -> dict:
         "status": status,
         "job_id": o.get("job_id"),
         "template_id": tid,
-        "design": {
+        "document": {
             "width": doc.get("width"),
             "height": doc.get("height"),
             "background": doc.get("background", "#ffffff"),
             "layers": doc.get("layers") or [],
-            "elements": elements,
+            "layerFolders": doc.get("layerFolders") or [],
+            "elements": doc.get("elements") or [],
         },
+        "assets": assets,
     }