Initial SvelteKit frontend port of windwiderstand.de

Full parity with Astro site: content rows, post/tag routes, pagination,
event badges + OSM map, comments, Live-Search via /api/search-index,
CMS image proxy, RSS, sitemap.

Deploy: Dockerfile + docker-compose.prod.yml + Gitea Actions workflow
to build + push to git.pm86.de registry and ssh-deploy to Contabo.

src/lib/ui/SidebarNav.svelte

@@ -0,0 +1,33 @@
+<script lang="ts">
+  /**
+   * @type {{ label: string; links: { href: string; label: string; active?: boolean }[] }[]}
+   */
+  let { groups = [] } = $props();
+</script>
+
+<nav aria-label="Seitennavigation" class="w-60 bg-stein-50 p-4">
+  {#each groups as group, i}
+    <div class="{i > 0 ? 'mt-6' : ''}">
+      <p
+        class="mb-2 text-xs font-medium uppercase tracking-wider text-stein-500"
+      >
+        {group.label}
+      </p>
+      <ul class="space-y-0">
+        {#each group.links as link}
+          <li>
+            <a
+              href={link.href}
+              class="block rounded-lg px-3 py-2 text-sm {link.active
+                ? 'bg-wald-50 font-medium text-wald-500'
+                : 'text-stein-700 hover:bg-wald-50'}"
+              aria-current={link.active ? 'page' : undefined}
+            >
+              {link.label}
+            </a>
+          </li>
+        {/each}
+      </ul>
+    </div>
+  {/each}
+</nav>