fix: Alpine.js defer race condition — blank pages on first load

Dynamic script creation (document.createElement) ignores the defer
attribute per HTML spec — scripts are async regardless. Alpine.js CDN
loaded fast and auto-initialized before page scripts had executed,
causing ReferenceError for x-data functions (adminStores, dark,
isSideMenuOpen, etc.) and blank pages.

Fix: Replace dynamic script creation with static <script defer> tags
and move extra_scripts block BEFORE Alpine.js in all 4 base templates
(admin, store, merchant, storefront). Alpine.js is now always the last
deferred script, ensuring all page functions are defined before it
auto-initializes.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

app/templates/storefront/base.html

@@ -380,28 +380,13 @@
     {# 6. API Client #}
     <script defer src="{{ url_for('static', path='shared/js/api-client.js') }}"></script>
 
-    {# 7. Alpine.js with CDN fallback (deferred - loads last) #}
-    <script>
-    (function() {
-        var script = document.createElement('script');
-        script.defer = true;
-        script.src = 'https://cdn.jsdelivr.net/npm/alpinejs@3.13.3/dist/cdn.min.js';
-
-        script.onerror = function() {
-            console.warn('Alpine.js CDN failed, loading local copy...');
-            var fallbackScript = document.createElement('script');
-            fallbackScript.defer = true;
-            fallbackScript.src = '{{ url_for("static", path="shared/js/lib/alpine.min.js") }}';
-            document.head.appendChild(fallbackScript);
-        };
-
-        document.head.appendChild(script);
-    })();
-    </script>
-
-    {# 8. Page-specific JavaScript #}
+    {# 7. Page-specific JavaScript (MUST load before Alpine.js) #}
     {% block extra_scripts %}{% endblock %}
 
+    {# 8. LAST: Alpine.js (must be last defer script — auto-initializes on load) #}
+    <script defer src="https://cdn.jsdelivr.net/npm/alpinejs@3.13.3/dist/cdn.min.js"
+            onerror="var s=document.createElement('script');s.defer=true;s.src='{{ url_for('static', path='shared/js/lib/alpine.min.js') }}';document.head.appendChild(s);"></script>
+
     {# Toast notification container #}
     <div id="toast-container" class="fixed bottom-4 right-4 z-50"></div>