Fix URL matcher for substr (vs strfry)

I wasn't able to reach https://nostr.kosmos.org/nodeinfo/2.1, which I
stumbled upon in an upstream PR. This one only matches exactly the paths
that substr is serving.

Tested/running in production.

site-cookbooks/kosmos_strfry/templates/nginx_conf_strfry.erb

@@ -25,7 +25,7 @@ server {
     alias /var/www/assets.kosmos.org/site/img/favicon.ico;
   }
 
-  location ~* ^/[@~n]|^/assets {
+  location ~ ^/(?:@|~|npub|naddr|nprofile|assets/) {
     proxy_set_header Host $host;
     proxy_set_header X-Real-IP $remote_addr;
     proxy_pass http://_substr;