feat(person): add a curator "Ereignis für diese Person" link to PersonCard

A curator on a person's page can now seed a timeline event from that
person: a gated link to #781's /zeitstrahl/events/new?personId={id},
which prefills the person and returns to /persons/{id} on save. Hidden
for a Reader. New i18n key person_add_event in de/en/es.

Refs #842
Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

frontend/src/routes/persons/[id]/PersonCard.svelte.spec.ts

@@ -0,0 +1,32 @@
+import { describe, it, expect, afterEach } from 'vitest';
+import { cleanup, render } from 'vitest-browser-svelte';
+import PersonCard from './PersonCard.svelte';
+
+afterEach(() => cleanup());
+
+const PERSON_ID = '55555555-5555-5555-5555-555555555555';
+
+const makePerson = (overrides = {}) => ({
+	id: PERSON_ID,
+	firstName: 'Karl',
+	lastName: 'Raddatz',
+	displayName: 'Karl Raddatz',
+	personType: 'PERSON',
+	...overrides
+});
+
+describe('PersonCard add-event affordance (#842)', () => {
+	it('shows an add-event link pre-seeded with the person to a curator (REQ-003)', () => {
+		render(PersonCard, { person: makePerson(), canWrite: true });
+		const add = document.querySelector(
+			'[data-testid="person-add-event"]'
+		) as HTMLAnchorElement | null;
+		expect(add).not.toBeNull();
+		expect(add?.getAttribute('href')).toBe(`/zeitstrahl/events/new?personId=${PERSON_ID}`);
+	});
+
+	it('renders no add-event link to a reader (REQ-004)', () => {
+		render(PersonCard, { person: makePerson(), canWrite: false });
+		expect(document.querySelector('[data-testid="person-add-event"]')).toBeNull();
+	});
+});