refactor(nav): replace static back-link hrefs with BackButton

All 7 in-scope back navigation links converted to use history.back().
Admin panel mobile chevron converted inline (icon-only, different
visual pattern). Cancel buttons left as static <a> links.

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

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

@@ -1,5 +1,6 @@
 <script lang="ts">
 import { m } from '$lib/paraglide/messages.js';
+import BackButton from '$lib/components/BackButton.svelte';
 
 let { data } = $props();
 
@@ -9,18 +10,7 @@ const count = $derived(documents.length);
 
 <div class="mx-auto max-w-4xl px-4 py-10">
 	<!-- Back Link -->
-	<a
-		href="/"
-		class="group mb-4 inline-flex items-center font-sans text-xs font-bold tracking-widest text-ink-2 uppercase transition-colors hover:text-ink"
-	>
-		<img
-			src="/degruyter-icons/Simple/Medium-24px/SVG/Action/Arrow/Arrow-Left-MD.svg"
-			alt=""
-			aria-hidden="true"
-			class="mr-2 h-4 w-4 transform transition-transform group-hover:-translate-x-1"
-		/>
-		{m.enrich_list_back()}
-	</a>
+	<BackButton />
 
 	<!-- Page Header -->
 	<div class="mb-8 flex items-center justify-between border-b border-line pb-6">