Fix 404 on static assets behind the regex location block

docker/nginx.conf

@@ -1,6 +1,6 @@
 server {
     listen 80;
-    server_name style.lvl0.xyz;
+    server_name _;   # behind a reverse proxy; match any Host
 
     location / {
         root /usr/share/nginx/html;
@@ -9,6 +9,7 @@ server {
     }
 
     location ~* \.(css|js|png|jpg|jpeg|gif|ico|svg|woff|woff2)$ {
+        root /usr/share/nginx/html;
         expires 1y;
         add_header Cache-Control "public, immutable";
     }