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/vendor-themes.html

@@ -1,22 +1,14 @@
 {# app/templates/admin/vendor-themes.html #}
 {% extends "admin/base.html" %}
+{% from 'shared/macros/headers.html' import page_header %}
+{% from 'shared/macros/alerts.html' import loading_state, error_state %}
 
 {% block title %}Vendor Themes{% endblock %}
 
 {% block alpine_data %}adminVendorThemes(){% endblock %}
 
 {% block content %}
-<!-- Page Header -->
-<div class="flex items-center justify-between my-6">
-    <div>
-        <h2 class="text-2xl font-semibold text-gray-700 dark:text-gray-200">
-            Vendor Themes
-        </h2>
-        <p class="text-sm text-gray-600 dark:text-gray-400 mt-1">
-            Customize vendor theme colors and branding
-        </p>
-    </div>
-</div>
+{{ page_header('Vendor Themes', subtitle='Customize vendor theme colors and branding') }}
 
 <!-- Vendor Selection -->
 <div class="px-4 py-6 mb-6 bg-white rounded-lg shadow-md dark:bg-gray-800">
@@ -44,20 +36,9 @@
     </div>
 </div>
 
-<!-- Loading State -->
-<div x-show="loading" class="text-center py-12">
-    <span x-html="$icon('spinner', 'inline w-8 h-8 text-purple-600')"></span>
-    <p class="mt-2 text-gray-600 dark:text-gray-400">Loading vendors...</p>
-</div>
+{{ loading_state('Loading vendors...') }}
 
-<!-- Error State -->
-<div x-show="error && !loading" class="mb-6 p-4 bg-red-100 border border-red-400 text-red-700 rounded-lg flex items-start">
-    <span x-html="$icon('exclamation', 'w-5 h-5 mr-3 mt-0.5 flex-shrink-0')"></span>
-    <div>
-        <p class="font-semibold">Error loading vendors</p>
-        <p class="text-sm" x-text="error"></p>
-    </div>
-</div>
+{{ error_state('Error loading vendors') }}
 
 <!-- Vendors List -->
 <div x-show="!loading && vendors.length > 0">