Fix nav links: map all app slugs to correct app URLs

Previously only 'cart' was mapped — slugs like 'federation', 'market',
'events', 'account' incorrectly linked to blog_url(). Now all app
slugs resolve to their proper cross-app URLs.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

browser/templates/_types/root/_nav.html

@@ -1,4 +1,10 @@
-{% set _app_slugs = {'cart': cart_url('/')} %}
+{% set _app_slugs = {
+  'cart': cart_url('/'),
+  'market': market_url('/'),
+  'events': events_url('/'),
+  'federation': federation_url('/'),
+  'account': account_url('/'),
+} %}
 {% set _first_seg = request.path.strip('/').split('/')[0] %}
 <div class="flex flex-col sm:flex-row sm:items-center gap-2 border-r border-stone-200 mr-2 sm:max-w-2xl"
      id="menu-items-nav-wrapper">