blog: Fix duplicates in author link href

The previous template chained the node directly into the filter
input string, producing hrefs like:

.../nodes/seed.radicle.dev/seed.radicle.dev users/did:key:…

The node appeared twice and a space replaced a slash. The root
cause was commit 6309f51, which refactored a hardcoded URL to use
the `explore` filter but passed the node via `append` instead of
as the filter's positional argument.

The fix assigns the node to a variable first and passes it to
`explore` directly, keeping the filter input to `users/<did>`.
Per-author node override continues to work.

Signed-off-by: Yorgos Saslis <yorgos.work@proton.me>

_layouts/blog.html

@@ -12,8 +12,9 @@
     <main>
       <h1>{{ page.title }}</h1>
       <p class="subtitle">{{ page.subtitle }}</p>
+      {% assign node = author.radicle.node | default: site.node %}
       <span class="author">
-	      Published by <a href="{{ author.radicle.node | default: site.node | append: ' users/' | append: author.radicle.did | explore }}">{{author.name}}</a>
+	      Published by <a href="{{ author.radicle.did | prepend: 'users/' | explore: node }}">{{author.name}}</a>
 	{% if author.atproto %}<a href="{{ author.atproto | prepend: "https://bsky.app/profile/" }}">🦋</a>{% endif %}
 	{% if author.fedi %}<a href="{{ author.fedi | fedi_to_https }}">🐘</a>{% endif %}
 	{% if author.web %}<a href="https://{{ author.web }}">🌐</a>{% endif %}