Fix IndieAuth client identification by making h-app visible

Following diagnosis in /docs/architecture/indieauth-client-diagnosis.md
and decision in /docs/decisions/ADR-006-indieauth-client-identification.md

Problem: The h-app microformat had hidden aria-hidden="true" attributes
that made it invisible to IndieAuth parsers, causing "client_id is not
registered" errors when authenticating with external providers.

Solution: Remove hidden attributes from h-app div in templates/base.html
to allow IndieAuth parsers to discover client metadata.

This ensures IndieAuth providers can validate our application during
the authorization flow.

Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude <noreply@anthropic.com>

templates/base.html

@@ -42,7 +42,7 @@
     <p>StarPunk v{{ config.get('VERSION', '0.5.0') }}</p>
 
     <!-- IndieAuth client discovery (h-app microformats) -->
-    <div class="h-app" hidden aria-hidden="true">
+    <div class="h-app">
       <a href="{{ config.SITE_URL }}" class="u-url p-name">{{ config.get('SITE_NAME', 'StarPunk') }}</a>
     </div>
   </footer>