fix(ui): use card-style save bar with mt-4 instead of full-bleed

Removes -mx-4 negative margin and switches to the card pattern
(rounded border, shadow-sm, mt-4) so the save bar matches the
width of the other cards on the edit page.

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

frontend/src/routes/persons/[id]/edit/PersonEditSaveBar.svelte

@@ -4,9 +4,8 @@ import { m } from '$lib/paraglide/messages.js';
 let { discardHref, formId }: { discardHref: string; formId?: 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)]"
+	class="mt-4 flex items-center justify-between rounded-sm border border-line bg-surface px-6 py-4 shadow-sm"
 >
 	<a href={discardHref} class="text-sm font-medium text-ink-2 transition-colors hover:text-ink">
 		{m.person_discard_changes()}