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