Increase default NGINX Unit request body limit to 100 MB in docker/nginx-unit.json

The current NGINX Unit configuration in netbox-docker implicitly limits
incoming HTTP request bodies to roughly 2.5 MB. This causes file uploads
(custom scripts, attachments, etc.) to fail with HTTP 413 before they
reach Django, even when NetBox settings like FILE_UPLOAD_MAX_MEMORY_SIZE
are raised.

This change adds a settings block to docker/nginx-unit.json to raise
the default limit:

{
  "settings": {
    "http": {
      "max_body_size": 104857600
    }
  }
}

With this change, new deployments can handle uploads up to 100 MB out
of the box, aligning the container default with the capabilities of
NetBox core and preventing unexpected 413 errors.

Fixes: https://github.com/netbox-community/netbox-docker/issues/897

docker/nginx-unit.json

@@ -73,5 +73,10 @@
       }
     }
   },
-  "access_log": "/dev/stdout"
+  "access_log": "/dev/stdout",
+  "settings": {
+    "http": {
+      "max_body_size": 104857600
+    }
+  }
 }