Cookie导出增加格式选择

- 后端: export接口增加 format 参数，支持 csv 和 custom 格式
- custom 格式: 账号----密码----ck，导出为 txt
- 后端: 导出用批量查 Account 替代逐条查询，消除 N+1
- 前端: 导出按钮改为下拉菜单可选格式
- 修复: blob 导出时不再取 .data（拦截器已提取）

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

web/backend/routers/cookies.py

@@ -65,28 +65,54 @@ def list_cookies(
 
 @router.get("/export")
 def export_cookies(
+    format: str = "csv",
     db: Session = Depends(get_db),
     current: User = Depends(require_permission("cookie:export")),
 ):
-    """导出 Cookie 为 CSV。"""
+    """导出 Cookie，支持 csv 和 custom 格式。
+    csv: 账号, Cookie, 时间
+    custom: 账号----密码----ck
+    """
     tasks = db.query(LoginTask).filter(
         LoginTask.status == "success"
     ).order_by(LoginTask.finished_at.desc()).all()
 
-    output = io.StringIO()
-    writer = csv.writer(output)
-    writer.writerow(["账号", "Cookie", "时间"])
+    # 批量查账号，避免 N+1
+    account_ids = [t.account_id for t in tasks]
+    accounts_map = {}
+    if account_ids:
+        accs = db.query(Account).filter(Account.id.in_(account_ids)).all()
+        accounts_map = {a.id: a for a in accs}
 
-    for t in tasks:
-        acc = db.query(Account).filter(Account.id == t.account_id).first()
-        username = acc.username if acc else ""
-        writer.writerow([username, t.cookie or "", _fmt_dt(t.finished_at) or ""])
+    if format == "custom":
+        # 账号----密码----ck
+        lines = []
+        for t in tasks:
+            acc = accounts_map.get(t.account_id)
+            username = acc.username if acc else ""
+            password = acc.password if acc else ""
+            ck = t.cookie or ""
+            lines.append(f"{username}----{password}----{ck}")
+        content = "\n".join(lines)
+        filename = "cookies_custom.txt"
+        media = "text/plain"
+    else:
+        # CSV: 账号, Cookie, 时间
+        output = io.StringIO()
+        writer = csv.writer(output)
+        writer.writerow(["账号", "Cookie", "时间"])
+        for t in tasks:
+            acc = accounts_map.get(t.account_id)
+            username = acc.username if acc else ""
+            writer.writerow([username, t.cookie or "", _fmt_dt(t.finished_at) or ""])
+        content = output.getvalue()
+        filename = "cookies.csv"
+        media = "text/csv"
 
-    output.seek(0)
     return StreamingResponse(
-        iter([output.getvalue()]),
-        media_type="text/csv",
-        headers={"Content-Disposition": "attachment; filename=cookies.csv"},
+        iter([content]),
+        media_type=media,
+        headers={"Content-Disposition": f"attachment; filename={filename}"},
     )