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/PersonEditSaveBar.svelte

@@ -0,0 +1,21 @@
+<script lang="ts">
+import { m } from '$lib/paraglide/messages.js';
+
+let { discardHref }: { discardHref: string } = $props();
+</script>
+
+<!-- Sticky full-bleed save bar -->
+<div
+	class="sticky bottom-0 z-10 -mx-4 flex items-center justify-between border-t border-line bg-surface px-6 py-4 shadow-[0_-2px_8px_rgba(0,0,0,0.06)]"
+>
+	<a href={discardHref} class="text-sm font-medium text-ink-2 transition-colors hover:text-ink">
+		{m.person_discard_changes()}
+	</a>
+	<button
+		type="submit"
+		formaction="?/update"
+		class="rounded bg-primary px-6 py-2 text-sm font-bold tracking-widest text-primary-fg uppercase transition-colors hover:bg-primary/80"
+	>
+		{m.btn_save()}
+	</button>
+</div>