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/persons/[id]/+page.svelte

@@ -1,6 +1,7 @@
 <script lang="ts">
 import { m } from '$lib/paraglide/messages.js';
 import { SvelteMap } from 'svelte/reactivity';
+import BackButton from '$lib/components/BackButton.svelte';
 import PersonCard from './PersonCard.svelte';
 import NameHistoryCard from './NameHistoryCard.svelte';
 import CoCorrespondentsList from './CoCorrespondentsList.svelte';
@@ -50,18 +51,7 @@ const coCorrespondents = $derived.by(() => {
 <div class="mx-auto max-w-6xl px-4 py-10">
 	<!-- Back Link -->
 	<div class="mb-6">
-		<a
-			href="/persons"
-			class="group inline-flex items-center 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.btn_back_to_overview()}
-		</a>
+		<BackButton />
 	</div>
 
 	<!-- 2-column layout on large screens -->