fix: use $icon() helper for spinner in testing dashboard

Replaces inline SVG with the centralized icon system for consistency.

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

app/templates/admin/testing-dashboard.html

@@ -28,10 +28,7 @@
     <div class="p-4 bg-purple-100 dark:bg-purple-900 rounded-lg shadow-xs">
         <div class="flex items-center justify-between">
             <div class="flex items-center">
-                <svg class="animate-spin h-5 w-5 text-purple-600 dark:text-purple-400 mr-3" xmlns="http://www.w3.org/2000/svg" fill="none" viewBox="0 0 24 24">
-                    <circle class="opacity-25" cx="12" cy="12" r="10" stroke="currentColor" stroke-width="4"></circle>
-                    <path class="opacity-75" fill="currentColor" d="M4 12a8 8 0 018-8V0C5.373 0 0 5.373 0 12h4zm2 5.291A7.962 7.962 0 014 12H0c0 3.042 1.135 5.824 3 7.938l3-2.647z"></path>
-                </svg>
+                <span x-html="$icon('spinner', 'h-5 w-5 text-purple-600 dark:text-purple-400 mr-3')"></span>
                 <div>
                     <p class="font-semibold text-purple-800 dark:text-purple-200">Running tests...</p>
                     <p class="text-sm text-purple-600 dark:text-purple-300">Tests are executing in the background. You can leave this page and come back.</p>