feat(posts): filter by year next to search

- Year dropdown derived from post.created, sorted desc
- Combines with search (AND); "Filter zurücksetzen" clears both
- Renamed isSearching→isFiltering to reflect combined state

src/components/BlogOverview.svelte

@@ -54,18 +54,40 @@
   } = $props();
 
   let query = $state("");
+  let year = $state<string>("");
   const normalizedQuery = $derived(query.trim().toLowerCase());
-  const isSearching = $derived(normalizedQuery.length >= 2);
+  const isFiltering = $derived(normalizedQuery.length >= 2 || year !== "");
 
-  const searchResults = $derived.by<SearchIndexEntry[]>(() => {
-    if (!isSearching || !searchIndex) return [];
+  function yearOf(entry: SearchIndexEntry): string {
+    const iso = entry.created ?? "";
+    if (!iso) return "";
+    const d = new Date(iso);
+    return Number.isNaN(d.getTime()) ? "" : String(d.getFullYear());
+  }
+
+  const availableYears = $derived.by<string[]>(() => {
+    if (!searchIndex) return [];
+    const set = new Set<string>();
+    for (const p of searchIndex) {
+      const y = yearOf(p);
+      if (y) set.add(y);
+    }
+    return Array.from(set).sort((a, b) => b.localeCompare(a));
+  });
+
+  const filteredResults = $derived.by<SearchIndexEntry[]>(() => {
+    if (!isFiltering || !searchIndex) return [];
     const q = normalizedQuery;
     return searchIndex
       .filter((p) => {
-        const hay = `${p.headline} ${p.excerpt} ${p.subheadline} ${p.tags.join(" ")}`.toLowerCase();
-        return hay.includes(q);
+        if (year && yearOf(p) !== year) return false;
+        if (q) {
+          const hay = `${p.headline} ${p.excerpt} ${p.subheadline} ${p.tags.join(" ")}`.toLowerCase();
+          if (!hay.includes(q)) return false;
+        }
+        return true;
       })
-      .slice(0, 40);
+      .slice(0, 80);
   });
 
   function searchResultHref(slug: string): string {
@@ -95,7 +117,7 @@
 
 <div class="blog-overview">
   {#if searchIndex}
-    <div class="mb-4">
+    <div class="mb-4 flex flex-wrap items-center gap-2">
       <label class="relative block w-full sm:max-w-sm">
         <span class="sr-only">Suche</span>
         <span class="pointer-events-none absolute top-1/2 left-2 -translate-y-1/2 text-zinc-500">
@@ -118,10 +140,30 @@
           </button>
         {/if}
       </label>
+      {#if availableYears.length > 0}
+        <label class="relative inline-flex items-center">
+          <span class="sr-only">Jahr</span>
+          <span class="pointer-events-none absolute top-1/2 left-2 -translate-y-1/2 text-zinc-500">
+            <Ico icon="mdi:calendar" class="h-4 w-4" />
+          </span>
+          <select
+            bind:value={year}
+            class="appearance-none rounded-sm border border-zinc-300 bg-white py-2 pr-7 pl-8 text-sm focus:border-zinc-500 focus:outline-none"
+          >
+            <option value="">Alle Jahre</option>
+            {#each availableYears as y}
+              <option value={y}>{y}</option>
+            {/each}
+          </select>
+          <span class="pointer-events-none absolute top-1/2 right-1.5 -translate-y-1/2 text-zinc-500">
+            <Ico icon="mdi:chevron-down" class="h-4 w-4" />
+          </span>
+        </label>
+      {/if}
     </div>
   {/if}
 
-  {#if !isSearching && upcomingEvents.length > 0}
+  {#if !isFiltering && upcomingEvents.length > 0}
     <section class="mb-6 rounded-sm border border-zinc-200 bg-zinc-50 p-4">
       <h2 class="mb-3 flex items-center gap-1.5 text-sm font-semibold tracking-wide text-zinc-700 uppercase">
         <Ico icon="mdi:calendar-clock" class="h-4 w-4" />
@@ -142,13 +184,23 @@
     </section>
   {/if}
 
-  {#if isSearching}
-    <div class="mb-3 text-xs text-zinc-600">
-      {searchResults.length} Treffer für „{query}"
+  {#if isFiltering}
+    <div class="mb-3 flex flex-wrap items-center gap-2 text-xs text-zinc-600">
+      <span>
+        {filteredResults.length}
+        {filteredResults.length === 1 ? "Treffer" : "Treffer"}
+        {#if query}für „{query}"{/if}
+        {#if year}im Jahr {year}{/if}
+      </span>
+      <button
+        type="button"
+        onclick={() => { query = ""; year = ""; }}
+        class="text-zinc-500 underline hover:text-zinc-900"
+      >Filter zurücksetzen</button>
     </div>
-    {#if searchResults.length > 0}
+    {#if filteredResults.length > 0}
       <div class="py-2 grid grid-cols-1 gap-4 sm:grid-cols-2 lg:grid-cols-3">
-        {#each searchResults as hit}
+        {#each filteredResults 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">