feat(persons): add /persons/[id]/edit route with PersonEditForm, PersonDangerZone

New edit route with WRITE_ALL guard; PersonEditForm (6 fields), sticky
PersonEditSaveBar, collapsed PersonDangerZone with PersonMergePanel.

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

frontend/src/routes/persons/[id]/edit/+page.svelte

@@ -0,0 +1,56 @@
+<script lang="ts">
+import { m } from '$lib/paraglide/messages.js';
+import { enhance } from '$app/forms';
+import PersonEditForm from './PersonEditForm.svelte';
+import PersonEditSaveBar from './PersonEditSaveBar.svelte';
+import PersonDangerZone from './PersonDangerZone.svelte';
+
+let { data, form } = $props();
+const person = $derived(data.person);
+</script>
+
+<div class="mx-auto max-w-2xl px-4 py-8">
+	<!-- Back link -->
+	<div class="mb-6">
+		<a
+			href="/persons/{person.id}"
+			class="group mb-4 inline-flex items-center text-xs font-bold tracking-widest text-ink-2 uppercase transition-colors hover:text-ink"
+		>
+			<svg
+				class="mr-2 h-4 w-4 transform transition-transform group-hover:-translate-x-1"
+				fill="none"
+				stroke="currentColor"
+				viewBox="0 0 24 24"
+			>
+				<path
+					stroke-linecap="round"
+					stroke-linejoin="round"
+					stroke-width="2"
+					d="M10 19l-7-7m0 0l7-7m-7 7h18"
+				/>
+			</svg>
+			{person.firstName}
+			{person.lastName}
+		</a>
+		<h1 class="font-serif text-3xl text-ink">{m.person_edit_heading()}</h1>
+	</div>
+
+	{#if form?.updateError}
+		<div class="mb-6 rounded border border-red-200 bg-red-50 p-4 text-red-700">
+			{form.updateError}
+		</div>
+	{/if}
+
+	<form method="POST" use:enhance>
+		<div class="rounded-sm border border-line bg-surface p-6 shadow-sm">
+			<h2 class="mb-5 text-xs font-bold tracking-widest text-ink-3 uppercase">
+				{m.persons_section_details()}
+			</h2>
+			<PersonEditForm person={person} />
+		</div>
+
+		<PersonDangerZone person={person} form={form} />
+
+		<PersonEditSaveBar discardHref="/persons/{person.id}" />
+	</form>
+</div>