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-edit.html

@@ -1,35 +1,20 @@
 {# app/templates/admin/vendor-edit.html #}
 {% extends "admin/base.html" %}
+{% from 'shared/macros/alerts.html' import loading_state %}
+{% from 'shared/macros/headers.html' import edit_page_header %}
 
 {% block title %}Edit Vendor{% endblock %}
 
 {% block alpine_data %}adminVendorEdit(){% 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">
-            Edit Vendor
-        </h2>
-        <p class="text-sm text-gray-600 dark:text-gray-400 mt-1" x-show="vendor">
-            <span x-text="vendor?.name"></span>
-            <span class="text-gray-400">•</span>
-            <span x-text="vendor?.vendor_code"></span>
-        </p>
-    </div>
-    <a href="/admin/vendors"
-       class="flex items-center 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-400 focus:outline-none">
-        <span x-html="$icon('arrow-left', 'w-4 h-4 mr-2')"></span>
-        Back to Vendors
-    </a>
-</div>
+{% call edit_page_header('Edit Vendor', '/admin/vendors', subtitle_show='vendor', back_label='Back to Vendors') %}
+    <span x-text="vendor?.name"></span>
+    <span class="text-gray-400">•</span>
+    <span x-text="vendor?.vendor_code"></span>
+{% endcall %}
 
-<!-- Loading State -->
-<div x-show="loadingVendor" 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 vendor...</p>
-</div>
+{{ loading_state('Loading vendor...', show_condition='loadingVendor') }}
 
 <!-- Edit Form -->
 <div x-show="!loadingVendor && vendor">