feat: implement admin-users management with super admin restriction

- Add /admin/admin-users routes for managing admin users (super admin only)
- Remove vendor role from user creation form (vendors created via company hierarchy)
- Add admin-users.html and admin-user-detail.html templates
- Add admin-users.js and admin-user-detail.js for frontend logic
- Move database operations to admin_platform_service (list, get, create, delete, toggle status)
- Update sidebar to show Admin Users section only for super admins
- Add isSuperAdmin computed property to init-alpine.js
- Fix /api/v1 prefix issues in JS files (apiClient already adds prefix)
- Update architecture rule JS-012 to catch more variable patterns (url, endpoint, path)
- Replace inline SVGs with $icon() helper in select-platform.html

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

app/templates/admin/partials/sidebar.html

@@ -66,12 +66,21 @@
         {{ menu_item('dashboard', '/admin/dashboard', 'home', 'Dashboard') }}
     </ul>
 
+    <!-- Super Admin Section (only visible to super admins) -->
+    <template x-if="isSuperAdmin">
+        <div>
+            {{ section_header('Super Admin', 'superAdmin') }}
+            {% call section_content('superAdmin') %}
+                {{ menu_item('admin-users', '/admin/admin-users', 'shield', 'Admin Users') }}
+            {% endcall %}
+        </div>
+    </template>
+
     <!-- Platform Administration Section -->
     {{ section_header('Platform Administration', 'platformAdmin') }}
     {% call section_content('platformAdmin') %}
         {{ menu_item('companies', '/admin/companies', 'office-building', 'Companies') }}
         {{ menu_item('vendors', '/admin/vendors', 'shopping-bag', 'Vendors') }}
-        {{ menu_item('users', '/admin/users', 'users', 'Users') }}
         {{ menu_item('messages', '/admin/messages', 'chat-bubble-left-right', 'Messages') }}
     {% endcall %}