feat: add unified /listening page and rename /funkwhale in nav

Navigation now includes both /listening (combined Last.fm + Funkwhale)
and /funkwhale (Funkwhale-only). Sidebar widget links to combined page.

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

_includes/components/sidebar.njk

@@ -214,7 +214,7 @@
   </div>
   {% endif %}
 
-  <a href="/funkwhale/" class="text-sm text-primary-600 dark:text-primary-400 hover:underline flex items-center gap-1">
+  <a href="/listening/" class="text-sm text-primary-600 dark:text-primary-400 hover:underline flex items-center gap-1">
     View full listening history
     <svg class="w-3 h-3" fill="none" stroke="currentColor" viewBox="0 0 24 24"><path stroke-linecap="round" stroke-linejoin="round" stroke-width="2" d="M9 5l7 7-7 7"/></svg>
   </a>

_includes/layouts/base.njk

@@ -97,7 +97,8 @@
           <a href="/notes/">Notes</a>
           <a href="/interactions/">Interactions</a>
           <a href="/github/">GitHub</a>
-          <a href="/funkwhale/">Listening</a>
+          <a href="/listening/">Listening</a>
+          <a href="/funkwhale/">Funkwhale</a>
           <a href="/youtube/">YouTube</a>
         </nav>
         <button id="theme-toggle" type="button" class="theme-toggle" aria-label="Toggle dark mode" title="Toggle dark mode">
@@ -121,7 +122,8 @@
       <a href="/notes/">Notes</a>
       <a href="/interactions/">Interactions</a>
       <a href="/github/">GitHub</a>
-      <a href="/funkwhale/">Listening</a>
+      <a href="/listening/">Listening</a>
+      <a href="/funkwhale/">Funkwhale</a>
       <a href="/youtube/">YouTube</a>
     </nav>
   </header>