refactor: 提取 requireUserId/requireUser/requireMembership 校验工具

- 新增 requireUserId：统一 14 处 userId 非空校验，返回 401
- 新增 requireUser：统一 4 处用户存在性检查，返回 404
- validateMembership 升级为 requireMembership，直接抛 403
- 混合校验拆分为 auth(401) + 字段(400)，状态码更准确

src/app/api/blindbox/room/[code]/route.ts

@@ -1,7 +1,7 @@
 import { NextResponse } from "next/server";
 import { prisma } from "@/lib/prisma";
 import { getRoomByCode } from "@/lib/blindbox";
-import { apiHandler, ApiError } from "@/lib/api";
+import { apiHandler, ApiError, requireUserId } from "@/lib/api";
 
 export const GET = apiHandler(async (_req, { params }) => {
   const { code } = await params;
@@ -26,7 +26,7 @@ export const DELETE = apiHandler(async (req, { params }) => {
   const { code } = await params;
   const { userId } = await req.json();
 
-  if (!userId) throw new ApiError("缺少用户 ID");
+  requireUserId(userId);
 
   const room = await prisma.blindBoxRoom.findUnique({
     where: { code: code.toUpperCase() },