refactor(#240): remove needsExpert feature completely

Drops the needsExpert / needs_expert flag end-to-end: DB migration
(V37, never applied), Document entity field, PATCH endpoint, service
method, DTO field, all three queue queries, ExpertBadge component,
i18n key, generated API types, and test fixture.

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

frontend/src/lib/components/SegmentationColumn.svelte

@@ -1,13 +1,11 @@
 <script lang="ts">
 import * as m from '$lib/paraglide/messages.js';
 import { getLocale } from '$lib/paraglide/runtime.js';
-import ExpertBadge from './ExpertBadge.svelte';
 
 type TranscriptionQueueItemDTO = {
 	id: string;
 	title: string;
 	documentDate?: string;
-	needsExpert: boolean;
 	annotationCount: number;
 	textedBlockCount: number;
 	reviewedBlockCount: number;
@@ -53,12 +51,7 @@ function formatDate(dateStr: string): string {
 						href="/documents/{doc.id}"
 						class="flex min-h-[44px] flex-col justify-center rounded px-1 py-2 hover:bg-canvas focus-visible:ring-2 focus-visible:ring-focus-ring focus-visible:ring-offset-2 focus-visible:outline-none"
 					>
-						<div class="flex flex-wrap items-center gap-1.5">
-							<span class="font-serif text-sm text-ink">{doc.title}</span>
-							{#if doc.needsExpert}
-								<ExpertBadge />
-							{/if}
-						</div>
+						<span class="font-serif text-sm text-ink">{doc.title}</span>
 						{#if doc.documentDate}
 							<span class="mt-0.5 text-xs text-ink-3">{formatDate(doc.documentDate)}</span>
 						{/if}