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.server.ts

@@ -0,0 +1,87 @@
+import { error, fail, redirect } from '@sveltejs/kit';
+import { createApiClient } from '$lib/api.server';
+import { getErrorMessage } from '$lib/errors';
+
+export async function load({ params, fetch, locals }) {
+	const canWrite =
+		(locals.user as { groups?: { permissions: string[] }[] } | undefined)?.groups?.some((g) =>
+			g.permissions.includes('WRITE_ALL')
+		) ?? false;
+
+	if (!canWrite) throw error(403, 'Forbidden');
+
+	const { id } = params;
+	const api = createApiClient(fetch);
+	const result = await api.GET('/api/persons/{id}', { params: { path: { id } } });
+
+	if (!result.response.ok) {
+		const code = (result.error as unknown as { code?: string })?.code;
+		throw error(result.response.status, getErrorMessage(code));
+	}
+
+	return { person: result.data! };
+}
+
+export const actions = {
+	update: async ({ request, params, fetch }) => {
+		const formData = await request.formData();
+		const firstName = formData.get('firstName')?.toString().trim();
+		const lastName = formData.get('lastName')?.toString().trim();
+		const alias = formData.get('alias')?.toString().trim() || undefined;
+		const notes = formData.get('notes')?.toString().trim() || undefined;
+		const birthYearStr = formData.get('birthYear')?.toString().trim();
+		const deathYearStr = formData.get('deathYear')?.toString().trim();
+		const birthYear = birthYearStr ? parseInt(birthYearStr, 10) : undefined;
+		const deathYear = deathYearStr ? parseInt(deathYearStr, 10) : undefined;
+
+		if (!firstName || !lastName) {
+			return fail(400, { updateError: 'Vor- und Nachname sind Pflichtfelder.' });
+		}
+
+		const api = createApiClient(fetch);
+		const result = await api.PUT('/api/persons/{id}', {
+			params: { path: { id: params.id } },
+			body: {
+				firstName,
+				lastName,
+				...(alias ? { alias } : {}),
+				...(notes ? { notes } : {}),
+				...(birthYear ? { birthYear } : {}),
+				...(deathYear ? { deathYear } : {})
+			}
+		});
+
+		if (!result.response.ok) {
+			const code = (result.error as unknown as { code?: string })?.code;
+			return fail(result.response.status, { updateError: getErrorMessage(code) });
+		}
+
+		throw redirect(303, `/persons/${params.id}`);
+	},
+
+	discard: async ({ params }) => {
+		throw redirect(303, `/persons/${params.id}`);
+	},
+
+	merge: async ({ request, params, fetch }) => {
+		const formData = await request.formData();
+		const targetPersonId = formData.get('targetPersonId')?.toString();
+
+		if (!targetPersonId) {
+			return fail(400, { mergeError: 'Bitte eine Zielperson auswählen.' });
+		}
+
+		const api = createApiClient(fetch);
+		const result = await api.POST('/api/persons/{id}/merge', {
+			params: { path: { id: params.id } },
+			body: { targetPersonId }
+		});
+
+		if (!result.response.ok) {
+			const code = (result.error as unknown as { code?: string })?.code;
+			return fail(result.response.status, { mergeError: getErrorMessage(code) });
+		}
+
+		throw redirect(303, `/persons/${targetPersonId}`);
+	}
+};