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-create.html

@@ -1,32 +1,16 @@
 {# app/templates/admin/vendor-create.html #}
 {% extends "admin/base.html" %}
+{% from 'shared/macros/headers.html' import page_header %}
+{% from 'shared/macros/alerts.html' import error_state %}
 
 {% block title %}Create Vendor{% endblock %}
 
 {% block alpine_data %}adminVendorCreate(){% 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">
-            Create New Vendor
-        </h2>
-        <p class="mt-1 text-sm text-gray-600 dark:text-gray-400">
-            Create a vendor (storefront/brand) under an existing company
-        </p>
-    </div>
-    <a
-        href="/admin/vendors"
-        class="px-4 py-2 text-sm font-medium leading-5 text-gray-700 transition-colors duration-150 bg-white border border-gray-300 rounded-lg dark:text-gray-400 dark:border-gray-600 dark:bg-gray-800 hover:border-gray-500 focus:outline-none focus:shadow-outline-gray"
-    >
-        <span class="flex items-center">
-            <span x-html="$icon('arrow-left', 'w-4 h-4 mr-2')"></span>
-            Back to Vendors
-        </span>
-    </a>
-</div>
+{{ page_header('Create New Vendor', subtitle='Create a vendor (storefront/brand) under an existing company', back_url='/admin/vendors', back_label='Back to Vendors') }}
 
+{# noqa: FE-003 - Custom success message with nested template #}
 <!-- Success Message -->
 <div x-show="successMessage" x-cloak class="mb-6 p-4 bg-green-100 border border-green-400 text-green-700 rounded-lg">
     <div class="flex items-start">
@@ -48,16 +32,7 @@
     </div>
 </div>
 
-<!-- Error Message -->
-<div x-show="errorMessage" x-cloak class="mb-6 p-4 bg-red-100 border border-red-400 text-red-700 rounded-lg">
-    <div class="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 Creating Vendor</p>
-            <p class="text-sm mt-1" x-text="errorMessage"></p>
-        </div>
-    </div>
-</div>
+{{ error_state('Error Creating Vendor', error_var='errorMessage', show_condition='errorMessage') }}
 
 <!-- Loading Companies -->
 <div x-show="loadingCompanies" class="mb-6 p-4 bg-blue-50 border border-blue-200 text-blue-700 rounded-lg">