Add account-nav-item and account-page fragment handlers (Phase 5)

Events now serves tickets/bookings nav links and page panels as
fragments for the account app.

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

templates/fragments/account_nav_items.html

@@ -0,0 +1,23 @@
+{# Account nav items: tickets + bookings links for the account dashboard #}
+<div class="relative nav-group">
+  <a href="{{ account_url('/tickets/') }}"
+     hx-get="{{ account_url('/tickets/') }}"
+     hx-target="#main-panel"
+     hx-select="{{ hx_select_search }}"
+     hx-swap="outerHTML"
+     hx-push-url="true"
+     class="{{styles.nav_button}}">
+    tickets
+  </a>
+</div>
+<div class="relative nav-group">
+  <a href="{{ account_url('/bookings/') }}"
+     hx-get="{{ account_url('/bookings/') }}"
+     hx-target="#main-panel"
+     hx-select="{{ hx_select_search }}"
+     hx-swap="outerHTML"
+     hx-push-url="true"
+     class="{{styles.nav_button}}">
+    bookings
+  </a>
+</div>