fix: remove all hx-get from cross-domain links

Converts remaining links.link() calls with cross-app URLs
to plain <a> tags: auth→cart orders, post_data→events,
calendars header→events.

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

suma_browser/templates/_types/auth/_nav.html

@@ -2,6 +2,8 @@
 {% call links.link(url_for('auth.newsletters'), hx_select_search, select_colours, True, aclass=styles.nav_button) %}
   newsletters
 {% endcall %}
-{% call links.link(cart_url('/orders/'), hx_select_search, select_colours, True, aclass=styles.nav_button) %}
-  orders
-{% endcall %}
+<div class="relative nav-group">
+  <a href="{{ cart_url('/orders/') }}" class="{{styles.nav_button}}">
+    orders
+  </a>
+</div>

suma_browser/templates/_types/calendars/header/_header.html

@@ -1,12 +1,10 @@
 {% import 'macros/links.html' as links %}
 {% macro header_row(oob=False) %}
   {% call links.menu_row(id='calendars-row', oob=oob) %}
-    {% call links.link(events_url('/calendars/'), hx_select_search) %}
+    <a href="{{ events_url('/calendars/') }}" class="flex gap-2 px-3 py-2 rounded whitespace-normal text-center break-words leading-snug">
       <i class="fa fa-calendar" aria-hidden="true"></i>
-      <div>
-        Calendars
-      </div>
-    {% endcall %}
+      <div>Calendars</div>
+    </a>
     {% call links.desktop_nav() %}    
       {% include '_types/calendars/_nav.html' %}
     {% endcall %}

suma_browser/templates/_types/post_data/header/_header.html

@@ -1,12 +1,10 @@
 {% import 'macros/links.html' as links %}
 {% macro header_row(oob=False) %}
   {% call links.menu_row(id='post_data-row', oob=oob) %}
-    {% call links.link(events_url('/calendars/'), hx_select_search) %}
-     <i class="fa fa-database" aria-hidden="true"></i>
-      <div>
-        data
-      </div>
-    {% endcall %}
+    <a href="{{ events_url('/calendars/') }}" class="flex gap-2 px-3 py-2 rounded whitespace-normal text-center break-words leading-snug">
+      <i class="fa fa-database" aria-hidden="true"></i>
+      <div>data</div>
+    </a>
     {% call links.desktop_nav() %}    
       {#% include '_types/post_data/_nav.html' %#}
     {% endcall %}