feat(frontend): render honest precision dates in detail, list and search

Wires formatDocumentDate/DocumentDate into the read sites: the document
detail top bar + metadata drawer (the drawer shows the visible "Originaltext:"
raw line for UNKNOWN/SEASON/APPROX), the search/list rows (DocumentRow,
mobile + desktop), and the document multi-select dropdown label. A MONTH or
SEASON document now reads "Juni 1916"/"Sommer 1916" everywhere instead of a
fabricated day.

Adds metaDatePrecision to the DocumentRow/DocumentMultiSelect test fixtures
(required on DocumentListItem since #671) and updates the multi-select label
assertion to the honest long date.

Refs #666

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

frontend/src/lib/document/DocumentRow.svelte

@@ -2,7 +2,7 @@
 import { goto } from '$app/navigation';
 import type { components } from '$lib/generated/api';
 import { applyOffsets } from '$lib/document/search';
-import { formatDate } from '$lib/shared/utils/date';
+import DocumentDate from './DocumentDate.svelte';
 import * as m from '$lib/paraglide/messages.js';
 import { bulkSelectionStore } from '$lib/document/bulkSelection.svelte';
 import ProgressRing from '$lib/shared/primitives/ProgressRing.svelte';
@@ -164,7 +164,16 @@ function safeTagColor(color: string | null | undefined): string {
 				<!-- Mobile-only metadata -->
 				<div class="mt-3 grid grid-cols-2 gap-x-4 gap-y-1 font-sans text-xs text-ink-2 sm:hidden">
 					<div>
-						{doc.documentDate ? formatDate(doc.documentDate) : '—'}
+						{#if doc.documentDate}
+							<DocumentDate
+								iso={doc.documentDate}
+								precision={doc.metaDatePrecision}
+								end={doc.metaDateEnd}
+								showRaw={false}
+							/>
+						{:else}
+							—
+						{/if}
 					</div>
 					<div class="flex items-start gap-2">
 						<ProgressRing percentage={item.completionPercentage} />
@@ -178,7 +187,16 @@ function safeTagColor(color: string | null | undefined): string {
 			<!-- Right column — desktop only -->
 			<div class="hidden flex-col gap-2 pl-4 font-sans text-sm text-ink-2 sm:flex sm:w-44 lg:w-56">
 				<div>
-					{doc.documentDate ? formatDate(doc.documentDate) : '—'}
+					{#if doc.documentDate}
+						<DocumentDate
+							iso={doc.documentDate}
+							precision={doc.metaDatePrecision}
+							end={doc.metaDateEnd}
+							showRaw={false}
+						/>
+					{:else}
+						—
+					{/if}
 				</div>
 				<div>
 					<span class="font-bold tracking-wide text-ink-3 uppercase">{m.docs_list_from()}</span>