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/WhoWhenSection.svelte

@@ -0,0 +1,142 @@
+<script lang="ts">
+import { onMount, untrack } from 'svelte';
+import PersonTypeahead from '$lib/components/PersonTypeahead.svelte';
+import PersonMultiSelect from '$lib/components/PersonMultiSelect.svelte';
+import FieldLabelBadge from './FieldLabelBadge.svelte';
+import { isoToGerman, handleGermanDateInput } from '$lib/utils/date';
+import { m } from '$lib/paraglide/messages.js';
+import type { components } from '$lib/generated/api';
+
+type Person = components['schemas']['Person'];
+
+let {
+	senderId = $bindable(''),
+	selectedReceivers = $bindable<Person[]>([]),
+	dateIso = $bindable(''),
+	initialDateIso = '',
+	initialLocation = '',
+	initialSenderName = '',
+	suggestedDateIso = '',
+	suggestedSenderName = '',
+	hideDate = false,
+	editMode = false
+}: {
+	senderId?: string;
+	selectedReceivers?: Person[];
+	dateIso?: string;
+	initialDateIso?: string;
+	initialLocation?: string;
+	initialSenderName?: string;
+	suggestedDateIso?: string;
+	suggestedSenderName?: string;
+	hideDate?: boolean;
+	editMode?: boolean;
+} = $props();
+
+// dateDisplay seeds from the bindable's value or initialDateIso once at mount
+// and is then user-driven. onMount runs exactly once, so this never stomps
+// the parent's dateIso on a later prop change.
+let dateDisplay = $state('');
+let dateDirty = $state(false);
+
+onMount(() => {
+	const seed = dateIso || initialDateIso;
+	if (seed) {
+		dateDisplay = isoToGerman(seed);
+		if (!dateIso) dateIso = seed;
+	}
+});
+
+const dateInvalid = $derived(dateDirty && dateDisplay.length > 0 && dateIso === '');
+
+function handleDateInput(e: Event) {
+	const result = handleGermanDateInput(e);
+	dateDisplay = result.display;
+	dateIso = result.iso;
+	dateDirty = true;
+}
+
+$effect(() => {
+	const suggested = suggestedDateIso;
+	if (suggested && !untrack(() => dateDirty)) {
+		dateDisplay = isoToGerman(suggested);
+		dateIso = suggested;
+	}
+});
+</script>
+
+<div class="rounded-sm border border-line bg-surface p-6 shadow-sm">
+	<h2 class="mb-5 text-xs font-bold tracking-widest text-ink-3 uppercase">
+		{m.doc_section_who_when()}
+	</h2>
+
+	<div class="grid grid-cols-1 gap-5 md:grid-cols-2">
+		{#if !hideDate}
+			<!-- Datum (required — row 1, col 1) -->
+			<div data-testid="who-when-date">
+				<label for="documentDate" class="mb-1 block text-sm font-medium text-ink-2"
+					>{m.form_label_date()}*</label
+				>
+				<input
+					id="documentDate"
+					type="text"
+					inputmode="numeric"
+					value={dateDisplay}
+					oninput={handleDateInput}
+					placeholder={m.form_placeholder_date()}
+					maxlength="10"
+					class="block w-full rounded border border-line px-2 py-3 text-sm shadow-sm
+                       {dateInvalid
+						? 'border-red-400 focus:outline-none focus-visible:ring-2 focus-visible:ring-red-500'
+						: 'focus:outline-none focus-visible:ring-2 focus-visible:ring-focus-ring'}"
+					aria-describedby={dateInvalid ? 'date-error' : undefined}
+				/>
+				<input type="hidden" name="documentDate" value={dateIso} />
+				{#if dateInvalid}
+					<p id="date-error" class="mt-1 text-xs text-red-600">{m.form_date_error()}</p>
+				{/if}
+			</div>
+		{/if}
+
+		<!-- Absender (required in upload mode — row 1, col 2) -->
+		<div>
+			<PersonTypeahead
+				name="senderId"
+				label={m.form_label_sender()}
+				required={!editMode}
+				bind:value={senderId}
+				initialName={initialSenderName}
+				suggestedName={suggestedSenderName}
+				badge={editMode ? 'replace' : undefined}
+			/>
+		</div>
+
+		<!-- Empfänger (optional — row 2, col 1) -->
+		<div>
+			<p class="mb-1 block text-sm font-medium text-ink-2">
+				{m.form_label_receivers()}
+				{#if editMode}<FieldLabelBadge variant="additive" />{/if}
+			</p>
+			<PersonMultiSelect bind:selectedPersons={selectedReceivers} />
+		</div>
+
+		{#if !editMode}
+			<!-- Ort (optional — row 2, col 2). Hidden in editMode: meta_location is
+				 NOT bulk-editable per the issue spec; the three editable location
+				 fields live in DescriptionSection. -->
+			<div>
+				<label for="location" class="mb-1 block text-sm font-medium text-ink-2"
+					>{m.form_label_location()}</label
+				>
+				<input
+					id="location"
+					type="text"
+					name="location"
+					value={initialLocation}
+					placeholder={m.form_placeholder_location()}
+					class="block w-full rounded border border-line px-2 py-3 text-sm shadow-sm focus:outline-none focus-visible:ring-2 focus-visible:ring-focus-ring"
+				/>
+			</div>
+		{/if}
+	</div>
+</div>