refactor: standardize admin templates with shared macros

Migrate all admin templates to use standardized components:
- Use tabs macros (tabs_nav, tab_button) for tab navigation
- Use number_stepper for quantity/numeric inputs
- Use headers macros for consistent page layouts
- Use modals macros for dialog components

Affected pages: dashboard, settings, logs, content-pages, companies,
vendors, users, imports, marketplace, code-quality, and more.

🤖 Generated with [Claude Code](https://claude.com/claude-code)

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

app/templates/admin/icons.html

@@ -1,5 +1,6 @@
 {# app/templates/admin/icons.html #}
 {% extends "admin/base.html" %}
+{% from 'shared/macros/headers.html' import page_header %}
 
 {% block title %}Icons Browser{% endblock %}
 
@@ -7,17 +8,7 @@
 {% block alpine_data %}adminIcons(){% endblock %}
 
 {% block content %}
-<!-- Page Header -->
-<div class="flex items-center justify-between my-6">
-    <h2 class="text-2xl font-semibold text-gray-700 dark:text-gray-200">
-        Icons Browser
-    </h2>
-    <a href="/admin/dashboard"
-       class="flex items-center px-4 py-2 text-sm font-medium text-gray-700 bg-white border border-gray-300 rounded-lg hover:bg-gray-50 dark:text-gray-300 dark:bg-gray-800 dark:border-gray-600 dark:hover:bg-gray-700">
-        <span x-html="$icon('arrow-left', 'w-4 h-4 mr-2')"></span>
-        Back to Dashboard
-    </a>
-</div>
+{{ page_header('Icons Browser', back_url='/admin/dashboard', back_label='Back to Dashboard') }}
 
 <!-- Introduction Card -->
 <div class="bg-gradient-to-r from-purple-600 to-indigo-600 rounded-lg shadow-lg p-6 mb-8">