refactor: move document domain core to lib/document/

Moves ~25 components, utils (search, filename, groupDocuments,
documentStatusLabel, validateFile), bulkSelection store, and
TranscriptionSection sub-component. Fixes broken relative imports.

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

frontend/src/lib/document/ThumbnailRow.svelte

@@ -0,0 +1,98 @@
+<script lang="ts">
+import ConversationThumbnail from '$lib/conversation/ConversationThumbnail.svelte';
+import TagChipList from '$lib/components/TagChipList.svelte';
+import { formatDate } from '$lib/utils/date';
+import * as m from '$lib/paraglide/messages.js';
+
+type Person = { id: string; firstName?: string | null; lastName: string; displayName: string };
+type Tag = { id: string; name: string };
+
+type Doc = {
+	id: string;
+	title?: string;
+	originalFilename: string;
+	documentDate?: string;
+	location?: string;
+	summary?: string;
+	contentType?: string;
+	thumbnailKey?: string;
+	thumbnailGeneratedAt?: string;
+	thumbnailAspect?: 'PORTRAIT' | 'LANDSCAPE';
+	pageCount?: number;
+	sender?: Person | null;
+	receivers?: Person[];
+	tags?: Tag[];
+};
+
+let {
+	doc,
+	isOut,
+	showOtherParty
+}: {
+	doc: Doc;
+	isOut: boolean;
+	showOtherParty: boolean;
+} = $props();
+
+const title = $derived(doc.title || doc.originalFilename);
+const otherPartyName = $derived(
+	showOtherParty
+		? isOut
+			? (doc.receivers?.[0]?.displayName ?? '')
+			: (doc.sender?.displayName ?? '')
+		: ''
+);
+const directionLabel = $derived(isOut ? m.row_direction_sent() : m.row_direction_received());
+const ariaLabel = $derived(
+	`${directionLabel}: ${title}${doc.documentDate ? `, ${formatDate(doc.documentDate)}` : ''}`
+);
+</script>
+
+<a
+	href={`/documents/${doc.id}`}
+	aria-label={ariaLabel}
+	class="group flex min-h-[120px] items-start gap-3 border-b border-l-[3px] border-line-2 px-[14px] py-[10px] transition-colors last:border-b-0 focus-within:bg-muted hover:bg-muted focus-visible:outline-2 focus-visible:outline-offset-[-2px] focus-visible:outline-primary"
+	class:border-l-primary={isOut}
+	class:border-l-accent={!isOut}
+>
+	<ConversationThumbnail doc={doc} />
+
+	<div class="flex min-w-0 flex-1 flex-col gap-1.5">
+		<div class="flex min-w-0 items-center gap-2">
+			<img
+				data-testid="thumb-row-direction-icon"
+				src={isOut
+					? '/degruyter-icons/Simple/Medium-24px/SVG/Action/Long-Arrow/Long-Arrow-Right-MD.svg'
+					: '/degruyter-icons/Simple/Medium-24px/SVG/Action/Long-Arrow/Long-Arrow-Left-MD.svg'}
+				alt=""
+				aria-hidden="true"
+				class="h-5 w-5 shrink-0 opacity-70"
+				class:text-primary={isOut}
+				class:text-accent={!isOut}
+			/>
+			<div class="min-w-0 flex-1 truncate text-lg font-bold text-ink">
+				{title}
+			</div>
+		</div>
+
+		{#if doc.summary}
+			<div class="line-clamp-2 text-base text-ink-2 italic">
+				&ldquo;{doc.summary}&rdquo;
+			</div>
+		{/if}
+
+		<div class="flex flex-wrap items-center gap-x-[6px] gap-y-1 text-sm text-ink-3">
+			<span>{doc.documentDate ? formatDate(doc.documentDate) : '—'}</span>
+			{#if doc.location}
+				<span class="text-line">·</span>
+				<span>{doc.location}</span>
+			{/if}
+			{#if otherPartyName}
+				<span class="text-line">·</span>
+				<span>{otherPartyName}</span>
+			{/if}
+		</div>
+
+		<TagChipList tags={doc.tags ?? []} />
+	</div>
+</a>