fix(web): /promotion 独立 try_files 防 SPA 误判；静态探测支持 Range 与 HTML 识别

Made-with: Cursor

deploy/web/default.conf

@@ -17,6 +17,12 @@ server {
     add_header Cache-Control "public, immutable";
   }
 
+  # 推广素材：文件必须真实存在，禁止落到 SPA index.html（否则前端误判「静态存在」、视频拿到 HTML）
+  location ^~ /promotion/ {
+    try_files $uri =404;
+    add_header Cache-Control "public, max-age=86400";
+  }
+
   location = / {
     try_files /index.html =404;
   }