feat(posts): search, upcoming events, RSS feed

- Client-side search on /posts/ (full archive, ~2-char threshold)
- Upcoming-events block at top of /posts/ from isEvent+eventDate posts
- RSS feed at /posts/rss.xml via @astrojs/rss
- Layout head: rss autodiscovery link
- RSS subscribe link below the listing
- Style tweaks on QuoteBlock and PostOverviewBlock

src/components/BlogOverview.svelte

@@ -14,6 +14,20 @@
     color?: string;
   }
 
+  type SearchIndexEntry = {
+    slug: string;
+    headline: string;
+    excerpt: string;
+    subheadline: string;
+    tags: string[];
+    image: string | null;
+    created: string | null;
+    isEvent: boolean;
+    eventDate: string | null;
+  };
+
+  type EventPost = PostEntry & { eventDate?: string; isEvent?: boolean };
+
   let {
     posts = [],
     tags = [],
@@ -23,6 +37,8 @@
     totalPosts = 0,
     basePath = "/posts",
     translations = {},
+    upcomingEvents = [],
+    searchIndex = null,
   }: {
     posts: PostEntry[];
     tags: TagEntry[];
@@ -32,8 +48,37 @@
     totalPosts?: number;
     basePath?: string;
     translations?: Translations | null;
+    upcomingEvents?: EventPost[];
+    searchIndex?: SearchIndexEntry[] | null;
   } = $props();
 
+  let query = $state("");
+  const normalizedQuery = $derived(query.trim().toLowerCase());
+  const isSearching = $derived(normalizedQuery.length >= 2);
+
+  const searchResults = $derived.by<SearchIndexEntry[]>(() => {
+    if (!isSearching || !searchIndex) return [];
+    const q = normalizedQuery;
+    return searchIndex
+      .filter((p) => {
+        const hay = `${p.headline} ${p.excerpt} ${p.subheadline} ${p.tags.join(" ")}`.toLowerCase();
+        return hay.includes(q);
+      })
+      .slice(0, 40);
+  });
+
+  function searchResultHref(slug: string): string {
+    const norm = (slug ?? "").replace(/^\//, "").trim();
+    return norm ? `/post/${encodeURIComponent(norm)}` : "/post";
+  }
+
+  function formatEventDate(iso: string | null | undefined): string {
+    if (!iso) return "";
+    const d = new Date(iso);
+    if (Number.isNaN(d.getTime())) return "";
+    return d.toLocaleDateString("de-DE", { day: "2-digit", month: "long", year: "numeric" });
+  }
+
   /** Immer Übersetzungen von der Astro-Seite nutzen (SSR + Insel), damit Keys wie blog_tag_all ankommen. */
   function t(key: string, replacements?: Record<string, string | number>) {
     return tStatic(translations ?? null, key, replacements);
@@ -48,6 +93,74 @@
 </script>
 
 <div class="blog-overview">
+  {#if searchIndex}
+    <div class="mb-4">
+      <label class="relative block">
+        <span class="sr-only">Suche</span>
+        <input
+          type="search"
+          bind:value={query}
+          placeholder="Beiträge durchsuchen…"
+          class="w-full rounded-sm border border-zinc-300 bg-white px-3 py-2 pr-10 text-sm focus:border-zinc-500 focus:outline-none"
+        />
+        {#if query}
+          <button
+            type="button"
+            onclick={() => (query = "")}
+            class="absolute top-1/2 right-2 -translate-y-1/2 text-zinc-500 hover:text-zinc-900"
+            aria-label="Suche leeren"
+          >×</button>
+        {/if}
+      </label>
+    </div>
+  {/if}
+
+  {#if !isSearching && upcomingEvents.length > 0}
+    <section class="mb-6 rounded-sm border border-zinc-200 bg-zinc-50 p-4">
+      <h2 class="mb-3 text-sm font-semibold tracking-wide text-zinc-700 uppercase">Nächste Termine</h2>
+      <ul class="space-y-2">
+        {#each upcomingEvents as ev}
+          <li>
+            <a href={postHref(ev)} class="group flex items-baseline gap-3 no-underline hover:underline">
+              <time class="shrink-0 text-xs font-medium text-zinc-600 tabular-nums">
+                {formatEventDate(ev.eventDate)}
+              </time>
+              <span class="text-sm text-zinc-900 group-hover:text-zinc-950">{ev.headline}</span>
+            </a>
+          </li>
+        {/each}
+      </ul>
+    </section>
+  {/if}
+
+  {#if isSearching}
+    <div class="mb-3 text-xs text-zinc-600">
+      {searchResults.length} Treffer für „{query}"
+    </div>
+    {#if searchResults.length > 0}
+      <div class="py-2 grid grid-cols-1 gap-4 sm:grid-cols-2 lg:grid-cols-3">
+        {#each searchResults as hit}
+          <a href={searchResultHref(hit.slug)} class="flex flex-col overflow-hidden border border-gray-200 bg-white text-slate-950 no-underline transition-all">
+            {#if hit.image}
+              <div class="aspect-3/2 w-full overflow-hidden bg-gray-100">
+                <img src={hit.image} alt={hit.headline} class="h-full w-full object-cover" loading="lazy" />
+              </div>
+            {/if}
+            <div class="flex flex-1 flex-col p-4">
+              <h3 class="mb-1 text-base font-semibold">{hit.headline}</h3>
+              {#if hit.excerpt}
+                <p class="text-sm text-zinc-700 line-clamp-3">{hit.excerpt}</p>
+              {/if}
+            </div>
+          </a>
+        {/each}
+      </div>
+    {:else}
+      <div class="rounded-sm border border-zinc-200 bg-white p-6 text-center text-sm text-zinc-600">
+        Keine Treffer. Versuche einen anderen Suchbegriff.
+      </div>
+    {/if}
+  {:else}
   {#if tags.length > 0}
     <div class="mb-2">
       <div class="flex flex-wrap gap-2" role="navigation" aria-label={t(T.blog_filter_aria)}>
@@ -117,4 +230,9 @@
       </div>
     </div>
   </div>
+
+  <div class="mt-4 text-xs text-zinc-600">
+    <a href="/posts/rss.xml" class="hover:underline">RSS-Feed abonnieren</a>
+  </div>
+  {/if}
 </div>