fix(ui): switch alias operations from client fetch to form actions

Replaces raw client-side fetch with SvelteKit form actions
(addAlias, removeAlias) using the server-side API client for
proper auth handling. 10 new component tests for NameHistoryEditCard.

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

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

@@ -86,5 +86,53 @@ export const actions = {
 		}
 
 		throw redirect(303, `/persons/${targetPersonId}`);
+	},
+
+	addAlias: async ({ request, params, fetch }) => {
+		const formData = await request.formData();
+		const lastName = formData.get('lastName')?.toString().trim();
+		const firstName = formData.get('firstName')?.toString().trim() || undefined;
+		const type = formData.get('type')?.toString();
+
+		if (!lastName) {
+			return fail(400, { aliasError: 'Nachname ist ein Pflichtfeld.' });
+		}
+		if (!type) {
+			return fail(400, { aliasError: 'Art ist ein Pflichtfeld.' });
+		}
+
+		const api = createApiClient(fetch);
+		const result = await api.POST('/api/persons/{id}/aliases', {
+			params: { path: { id: params.id } },
+			body: { lastName, firstName, type: type as 'BIRTH' | 'WIDOWED' | 'DIVORCED' | 'OTHER' }
+		});
+
+		if (!result.response.ok) {
+			const code = (result.error as unknown as { code?: string })?.code;
+			return fail(result.response.status, { aliasError: getErrorMessage(code) });
+		}
+
+		return { aliasSuccess: true };
+	},
+
+	removeAlias: async ({ request, params, fetch }) => {
+		const formData = await request.formData();
+		const aliasId = formData.get('aliasId')?.toString();
+
+		if (!aliasId) {
+			return fail(400, { aliasError: 'Alias ID fehlt.' });
+		}
+
+		const api = createApiClient(fetch);
+		const result = await api.DELETE('/api/persons/{id}/aliases/{aliasId}', {
+			params: { path: { id: params.id, aliasId } }
+		});
+
+		if (!result.response.ok) {
+			const code = (result.error as unknown as { code?: string })?.code;
+			return fail(result.response.status, { aliasError: getErrorMessage(code) });
+		}
+
+		return { aliasSuccess: true };
 	}
 };