fix: key threads on the canonical URL, and space the header box

SITEURL is empty in this config, so rendering the thread key into the template
produced a relative path. Threads would have been keyed on /pastfetch.html and
orphaned the moment the site moved or gained a prefix. The page computes
location.origin + location.pathname instead, which is unambiguous and needs no
configuration.

The fill in the REPLIES header ran straight into the count, which read as
'────0 messages'. Every other box on the board keeps a space there.

randogoth.com/bbs/templates/article.html

@@ -26,7 +26,6 @@
     JS the section simply is not there, which is honest, and the capsule never
     sees it at all since Gemini has no way to render it. -#}
 {%- if COMMENTS_HOST %}
-<div id="replies" data-host="{{ COMMENTS_HOST }}" data-site="{{ COMMENTS_SITE }}"
-     data-url="{{ SITEURL }}/{{ article.url }}"></div>
+<div id="replies" data-host="{{ COMMENTS_HOST }}" data-site="{{ COMMENTS_SITE }}"></div>
 {%- endif %}
 {% endblock %}