fix(stammbaum): add × dismiss button with aria-label to StammbaumSidePanel

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

frontend/src/lib/components/StammbaumSidePanel.svelte

@@ -139,13 +139,32 @@ const topDerived = $derived(
 </script>
 
 <div class="flex h-full flex-col p-5">
-	<div class="mb-4">
-		<h2 class="font-serif text-lg text-ink">{node.displayName}</h2>
-		{#if node.birthYear || node.deathYear}
-			<p class="font-sans text-xs text-ink-3">
-				{node.birthYear ?? '?'}–{node.deathYear ?? ''}
-			</p>
-		{/if}
+	<div class="mb-4 flex items-start justify-between gap-2">
+		<div class="min-w-0">
+			<h2 class="font-serif text-lg text-ink">{node.displayName}</h2>
+			{#if node.birthYear || node.deathYear}
+				<p class="font-sans text-xs text-ink-3">
+					{node.birthYear ?? '?'}–{node.deathYear ?? ''}
+				</p>
+			{/if}
+		</div>
+		<button
+			type="button"
+			onclick={onClose}
+			aria-label={m.comp_dismiss()}
+			class="shrink-0 rounded-sm p-1 text-ink-3 transition hover:bg-muted hover:text-ink focus-visible:ring-2 focus-visible:ring-focus-ring focus-visible:outline-none"
+		>
+			<svg
+				class="h-4 w-4"
+				viewBox="0 0 16 16"
+				fill="none"
+				stroke="currentColor"
+				stroke-width="2"
+				aria-hidden="true"
+			>
+				<path stroke-linecap="round" d="M3 3l10 10M13 3L3 13" />
+			</svg>
+		</button>
 	</div>
 
 	{#if error}