feat: lazy load learning map images

nginx.conf

@@ -9,6 +9,14 @@ server {
         try_files $uri $uri/ /index.html;
     }
 
+    # 一图流图片目录，由 Docker 挂载提供，支持运行时新增图片
+    location /learning-images/ {
+        alias /usr/share/nginx/html/learning-images/;
+        autoindex on;
+        charset utf-8;
+        add_header Cache-Control "no-store";
+    }
+
     # 静态资源缓存
     location /assets {
         expires 1y;