feat(layout): finalize p01 and p02 changes

Complete UI foundation and app layout implementation, stabilize container health checks, and archive both OpenSpec changes after verification.

frontend/src/lib/components/layout/SidebarSection.svelte

@@ -0,0 +1,21 @@
+<script lang="ts">
+  import type { NavSection } from '$lib/types/layout';
+  import SidebarItem from './SidebarItem.svelte';
+
+  export let section: NavSection;
+  export let expanded = true;
+</script>
+
+<section class="px-2 py-1" data-testid="sidebar-section">
+  {#if expanded}
+    <h3 class="text-xs font-semibold uppercase tracking-wide text-base-content/60 px-2 py-2">
+      {section.title}
+    </h3>
+  {/if}
+
+  <div class="space-y-1">
+    {#each section.items as item (item.href)}
+      <SidebarItem icon={item.icon} label={item.label} href={item.href} {expanded} />
+    {/each}
+  </div>
+</section>