feat: add smooth scroll-to-top button with Alpine transition

partials/scroll-top.hbs

@@ -0,0 +1,16 @@
+<button 
+    x-show="showScrollTop"
+    x-transition:enter="transition ease-out duration-300"
+    x-transition:enter-start="opacity-0 translate-y-10"
+    x-transition:enter-end="opacity-100 translate-y-0"
+    x-transition:leave="transition ease-in duration-300"
+    x-transition:leave-start="opacity-100 translate-y-0"
+    x-transition:leave-end="opacity-0 translate-y-10"
+    @click="window.scrollTo({ top: 0, behavior: 'smooth' })"
+    class="fixed bottom-8 right-8 z-40 p-3 rounded-lg shadow-xl bg-[var(--brand-primary)] text-[var(--bg-primary)] hover:bg-[var(--brand-secondary)] hover:scale-110 active:scale-95 transition-all duration-300 group"
+    aria-label="Scroll to top"
+    x-cloak>
+    <svg xmlns="http://www.w3.org/2000/svg" fill="none" viewBox="0 0 24 24" stroke-width="2.5" stroke="currentColor" class="w-6 h-6 transform group-hover:-translate-y-1 transition-transform duration-300">
+        <path stroke-linecap="round" stroke-linejoin="round" d="M4.5 10.5 12 3m0 0 7.5 7.5M12 3v18" />
+    </svg>
+</button>