fix(persons): localize validation error messages via Paraglide i18n

validatePersonFields now returns a PersonValidationKey instead of a
hardcoded German string. resolveValidationMessage() translates the key
through Paraglide so English and Spanish locale users no longer see
German error text. Adds validation_last_name_required and
validation_first_name_required to all three message files.

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

frontend/messages/de.json

@@ -540,6 +540,8 @@
 	"person_alias_btn_delete": "Entfernen",
 	"error_alias_not_found": "Der Namensalias wurde nicht gefunden.",
 	"error_invalid_person_type": "Der angegebene Personentyp ist ungültig.",
+	"validation_last_name_required": "Nachname ist Pflichtfeld.",
+	"validation_first_name_required": "Vorname ist Pflichtfeld.",
 	"error_ocr_service_unavailable": "Der OCR-Dienst ist nicht verfügbar.",
 	"error_ocr_job_not_found": "Der OCR-Auftrag wurde nicht gefunden.",
 	"error_ocr_document_not_uploaded": "Das Dokument hat keine Datei — OCR ist nicht möglich.",

frontend/messages/en.json

@@ -540,6 +540,8 @@
 	"person_alias_btn_delete": "Remove",
 	"error_alias_not_found": "The name alias was not found.",
 	"error_invalid_person_type": "The specified person type is not valid.",
+	"validation_last_name_required": "Last name is required.",
+	"validation_first_name_required": "First name is required.",
 	"error_ocr_service_unavailable": "The OCR service is not available.",
 	"error_ocr_job_not_found": "The OCR job was not found.",
 	"error_ocr_document_not_uploaded": "The document has no file — OCR is not possible.",

frontend/messages/es.json

@@ -540,6 +540,8 @@
 	"person_alias_btn_delete": "Eliminar",
 	"error_alias_not_found": "No se encontro el alias de nombre.",
 	"error_invalid_person_type": "El tipo de persona especificado no es válido.",
+	"validation_last_name_required": "El apellido es obligatorio.",
+	"validation_first_name_required": "El nombre es obligatorio.",
 	"error_ocr_service_unavailable": "El servicio OCR no está disponible.",
 	"error_ocr_job_not_found": "No se encontró el trabajo OCR.",
 	"error_ocr_document_not_uploaded": "El documento no tiene archivo — OCR no es posible.",

frontend/src/lib/person-validation.test.ts

@@ -6,22 +6,24 @@ describe('validatePersonFields', () => {
 		expect(validatePersonFields('PERSON', 'Hans', 'Müller')).toBeNull();
 	});
 
-	it('returns lastName error when lastName is missing', () => {
-		expect(validatePersonFields('PERSON', 'Hans', '')).toBe('Nachname ist Pflichtfeld.');
+	it('returns lastName error key when lastName is missing', () => {
+		expect(validatePersonFields('PERSON', 'Hans', '')).toBe('validation_last_name_required');
 	});
 
-	it('returns lastName error when lastName is undefined', () => {
+	it('returns lastName error key when lastName is undefined', () => {
 		expect(validatePersonFields('INSTITUTION', undefined, undefined)).toBe(
-			'Nachname ist Pflichtfeld.'
+			'validation_last_name_required'
 		);
 	});
 
-	it('returns firstName error when type is PERSON and firstName is missing', () => {
-		expect(validatePersonFields('PERSON', '', 'Müller')).toBe('Vorname ist Pflichtfeld.');
+	it('returns firstName error key when type is PERSON and firstName is missing', () => {
+		expect(validatePersonFields('PERSON', '', 'Müller')).toBe('validation_first_name_required');
 	});
 
-	it('returns firstName error when type is PERSON and firstName is undefined', () => {
-		expect(validatePersonFields('PERSON', undefined, 'Müller')).toBe('Vorname ist Pflichtfeld.');
+	it('returns firstName error key when type is PERSON and firstName is undefined', () => {
+		expect(validatePersonFields('PERSON', undefined, 'Müller')).toBe(
+			'validation_first_name_required'
+		);
 	});
 
 	it('returns null for INSTITUTION without firstName', () => {

frontend/src/lib/person-validation.ts

@@ -1,3 +1,5 @@
+import { m } from '$lib/paraglide/messages.js';
+
 export const PERSON_TYPES = ['PERSON', 'INSTITUTION', 'GROUP', 'UNKNOWN'] as const;
 export type PersonType = (typeof PERSON_TYPES)[number];
 
@@ -5,12 +7,22 @@ export function normalizePersonType(raw: string | undefined | null): PersonType
 	return raw === 'SKIP' ? 'UNKNOWN' : ((raw ?? 'PERSON') as PersonType);
 }
 
+export type PersonValidationKey =
+	| 'validation_last_name_required'
+	| 'validation_first_name_required';
+
+export function resolveValidationMessage(key: PersonValidationKey): string {
+	return key === 'validation_last_name_required'
+		? m.validation_last_name_required()
+		: m.validation_first_name_required();
+}
+
 export function validatePersonFields(
 	personType: string,
 	firstName: string | undefined | null,
 	lastName: string | undefined | null
-): string | null {
-	if (!lastName) return 'Nachname ist Pflichtfeld.';
-	if (personType === 'PERSON' && !firstName) return 'Vorname ist Pflichtfeld.';
+): PersonValidationKey | null {
+	if (!lastName) return 'validation_last_name_required';
+	if (personType === 'PERSON' && !firstName) return 'validation_first_name_required';
 	return null;
 }

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

@@ -1,7 +1,11 @@
 import { error, fail, redirect } from '@sveltejs/kit';
 import { createApiClient } from '$lib/api.server';
 import { getErrorMessage } from '$lib/errors';
-import { normalizePersonType, validatePersonFields } from '$lib/person-validation';
+import {
+	normalizePersonType,
+	validatePersonFields,
+	resolveValidationMessage
+} from '$lib/person-validation';
 
 export async function load({ params, fetch, locals }) {
 	const canWrite =
@@ -42,9 +46,9 @@ export const actions = {
 		const birthYear = birthYearStr ? parseInt(birthYearStr, 10) : undefined;
 		const deathYear = deathYearStr ? parseInt(deathYearStr, 10) : undefined;
 
-		const validationError = validatePersonFields(personType, firstName, lastName);
-		if (validationError) {
-			return fail(400, { updateError: validationError });
+		const validationKey = validatePersonFields(personType, firstName, lastName);
+		if (validationKey) {
+			return fail(400, { updateError: resolveValidationMessage(validationKey) });
 		}
 
 		const api = createApiClient(fetch);

frontend/src/routes/persons/new/+page.server.ts

@@ -1,7 +1,11 @@
 import { error, fail, redirect } from '@sveltejs/kit';
 import { createApiClient } from '$lib/api.server';
 import { getErrorMessage } from '$lib/errors';
-import { normalizePersonType, validatePersonFields } from '$lib/person-validation';
+import {
+	normalizePersonType,
+	validatePersonFields,
+	resolveValidationMessage
+} from '$lib/person-validation';
 
 export async function load({ locals }: { locals: App.Locals }) {
 	const canWrite =
@@ -23,10 +27,10 @@ export const actions = {
 		const deathYearStr = formData.get('deathYear')?.toString().trim();
 		const notes = formData.get('notes')?.toString().trim() || undefined;
 
-		const validationError = validatePersonFields(personType, firstName, lastName);
-		if (validationError) {
+		const validationKey = validatePersonFields(personType, firstName, lastName);
+		if (validationKey) {
 			return fail(400, {
-				error: validationError,
+				error: resolveValidationMessage(validationKey),
 				personType,
 				title,
 				firstName: firstName ?? '',