feat: add fission package download

backend/app/api/v1/fission.py

@@ -11,11 +11,12 @@ import logging
 from typing import Annotated
 
 from fastapi import APIRouter, Depends
+from fastapi.responses import FileResponse
 from pydantic import BaseModel, Field
 from sqlalchemy.orm import Session
 
 from app.core.database import get_db
-from app.core.response import ok, raise_not_found
+from app.core.response import ok, raise_business, raise_not_found
 from app.middleware.workspace_guard import CurrentUser, require_write_permission
 from app.models.fission import FissionTask, FissionNote
 
@@ -117,6 +118,40 @@ def get_fission_notes(
                "fanout_count": ft.fanout_count, "notes": notes})
 
 
+@router.get("/fission/{fission_id}/download")
+def download_fission_package(
+    fission_id: int,
+    current_user: Annotated[CurrentUser, Depends(require_write_permission)] = None,
+    db: Session = Depends(get_db),
+):
+    """下载裂变结果：把 N 套裂变笔记打成 zip（文案+图片+发布清单）。"""
+    ft = db.query(FissionTask).filter(
+        FissionTask.id == fission_id,
+        FissionTask.workspace_id == current_user.workspace_id,
+    ).first()
+    if not ft:
+        raise_not_found("裂变任务不存在")
+
+    rows = db.query(FissionNote).filter(
+        FissionNote.fission_id == fission_id,
+        FissionNote.workspace_id == current_user.workspace_id,
+    ).order_by(FissionNote.seq.asc()).all()
+    if not rows:
+        raise_business("裂变结果为空，暂不能下载")
+
+    from app.services.fission_package_exporter import build_fission_package
+    try:
+        zip_path = build_fission_package(ft, rows)
+    except ValueError as exc:
+        raise_business(str(exc))
+
+    return FileResponse(
+        path=zip_path,
+        media_type="application/zip",
+        filename=f"fission-{fission_id}.zip",
+    )
+
+
 @router.post("/fission/{fission_id}/notes/{seq}/retry-images")
 def retry_fission_note_images_endpoint(
     fission_id: int,