fix(web): 首屏产品视频在 VITE_PROMOTION_API_ONLY 时走 promotion-media，避免误请求 /promotion/ 404

Made-with: Cursor

web/src/data/promotionVideos.js

@@ -109,10 +109,20 @@ export async function pickPromotionAssetUrl(siteId, relPath) {
 }
 
 /**
- * 同步列表：全部静态 URL（首屏占位、无 siteId 时与异步结果一致场景）
- * @param {string} [_siteId] 保留兼容，当前忽略
+ * 同步列表：首屏占位（须与 buildPromotionVideosAsync 一致，避免 apiOnly 时先请求一堆 /promotion/ 404）
+ * @param {string} [siteId] 来自缓存的 site_id；会与 defaultWebSiteId 合并
  */
-export function buildPromotionVideos(_siteId) {
+export function buildPromotionVideos(siteId) {
+  const sid = String(siteId || defaultWebSiteId || '').trim()
+  if (apiOnly && sid) {
+    return PROMOTION_VIDEOS_BASE.map((v) => ({
+      id: v.id,
+      title: v.title,
+      desc: v.desc,
+      cover: promotionMediaApiUrl(sid, v.relCover),
+      src: promotionMediaApiUrl(sid, v.relVideo)
+    }))
+  }
   return PROMOTION_VIDEOS_BASE.map((v) => ({
     id: v.id,
     title: v.title,