fix: replace remaining hardcoded brand-navy/white tokens with semantic tokens

Fixes dark mode in enrich/done page (bg-white → bg-surface, text-brand-navy → text-ink,
border-brand-sand → border-line), enrich/[id] skip button (text-brand-navy/60 → text-ink-2),
and PanelHistory version list (divide-brand-sand → divide-line).

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

frontend/src/lib/components/PanelHistory.svelte

@@ -406,7 +406,7 @@ $effect(() => {
 			{/if}
 		{:else}
 			<!-- Version list with inline diff below each selected item -->
-			<ul class="divide-brand-sand divide-y">
+			<ul class="divide-y divide-line">
 				{#each versions as v, i (v.id)}
 					<li>
 						<button

frontend/src/routes/enrich/[id]/+page.svelte

@@ -135,7 +135,7 @@ let selectedReceivers = $state(untrack(() => doc.receivers ?? []));
 				<button
 					type="submit"
 					form="skip-form"
-					class="font-sans text-sm font-medium text-brand-navy/60 transition-colors hover:text-brand-navy"
+					class="font-sans text-sm font-medium text-ink-2 transition-colors hover:text-ink"
 				>
 					{m.enrich_skip()}
 				</button>

frontend/src/routes/enrich/done/+page.svelte

@@ -4,7 +4,7 @@ import { m } from '$lib/paraglide/messages.js';
 
 <div class="mx-auto max-w-4xl px-4 py-10">
 	<div
-		class="border-brand-sand flex flex-col items-center justify-center rounded-sm border bg-white py-20 text-center shadow-sm"
+		class="flex flex-col items-center justify-center rounded-sm border border-line bg-surface py-20 text-center shadow-sm"
 	>
 		<img
 			src="/degruyter-icons/Simple/Large-32px/SVG/Action/Check/Check-Double-LG.svg"
@@ -13,7 +13,7 @@ import { m } from '$lib/paraglide/messages.js';
 			class="mb-6 h-16 w-16"
 		/>
 
-		<h1 class="font-serif text-2xl font-medium text-brand-navy">
+		<h1 class="font-serif text-2xl font-medium text-ink">
 			{m.enrich_done_heading()}
 		</h1>