add .mjs MIME type to nginx to fix NS_ERROR_CORRUPTED_CONTENT

nginx doesn't know .mjs by default and serves it as
application/octet-stream, which breaks ES module loading
and causes Caddy compression mismatches.

nextcloud/nginx.conf

@@ -15,6 +15,11 @@ server {
     listen 80;
     server_name _;
 
+    include mime.types;
+    types {
+        application/javascript mjs;
+    }
+
     client_max_body_size 10G;
     client_body_timeout 300s;
     fastcgi_buffers 64 4K;