feat(dashboard): add EnrichmentBlock wrapper component

Composes UploadSuccessBanner + DashboardNeedsMetadata and reserves a
360px skeleton while \$navigating re-runs the loader with a fresh
incomplete list. Prevents the layout-shift jump after a batch upload
(Leonie's resolved decision #3 on issue #296).

Renders nothing when there is nothing to show — keeps the clean empty
dashboard.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

frontend/src/lib/components/EnrichmentBlock.svelte

@@ -0,0 +1,39 @@
+<script lang="ts">
+import { navigating } from '$app/stores';
+import DashboardNeedsMetadata from './DashboardNeedsMetadata.svelte';
+import UploadSuccessBanner from './UploadSuccessBanner.svelte';
+
+type IncompleteDoc = {
+	id: string;
+	title: string;
+	uploadedAt: string;
+};
+
+interface Props {
+	topDocs: IncompleteDoc[];
+	totalCount: number;
+	bannerCount: number;
+	onBannerClose: () => void;
+}
+
+let { topDocs, totalCount, bannerCount, onBannerClose }: Props = $props();
+
+const showSkeleton = $derived(!!$navigating && topDocs.length === 0);
+const showBlock = $derived(topDocs.length > 0 || bannerCount > 0 || showSkeleton);
+</script>
+
+{#if showBlock}
+	<div data-testid="enrichment-block" class="flex flex-col gap-3">
+		{#if bannerCount > 0}
+			<UploadSuccessBanner count={bannerCount} onClose={onBannerClose} />
+		{/if}
+		{#if topDocs.length > 0}
+			<DashboardNeedsMetadata topDocs={topDocs} totalCount={totalCount} />
+		{:else if showSkeleton}
+			<div
+				class="h-[360px] animate-pulse rounded-sm border border-line bg-surface/50 motion-reduce:animate-none"
+				aria-hidden="true"
+			></div>
+		{/if}
+	</div>
+{/if}