feat(persons): add INVALID_PERSON_TYPE error code with i18n translations

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

frontend/src/lib/errors.ts

@@ -7,6 +7,7 @@ import * as m from '$lib/paraglide/messages.js';
 export type ErrorCode =
 	| 'PERSON_NOT_FOUND'
 	| 'ALIAS_NOT_FOUND'
+	| 'INVALID_PERSON_TYPE'
 	| 'DOCUMENT_NOT_FOUND'
 	| 'DOCUMENT_NO_FILE'
 	| 'FILE_NOT_FOUND'
@@ -73,6 +74,8 @@ export function getErrorMessage(code: ErrorCode | string | undefined): string {
 			return m.error_person_not_found();
 		case 'ALIAS_NOT_FOUND':
 			return m.error_alias_not_found();
+		case 'INVALID_PERSON_TYPE':
+			return m.error_invalid_person_type();
 		case 'DOCUMENT_NOT_FOUND':
 			return m.error_document_not_found();
 		case 'DOCUMENT_NO_FILE':