feat(i18n): add BATCH_TOO_LARGE error code + 16 bulk-upload Paraglide keys

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

frontend/src/lib/errors.ts

@@ -41,6 +41,7 @@ export type ErrorCode =
 	| 'UNAUTHORIZED'
 	| 'FORBIDDEN'
 	| 'VALIDATION_ERROR'
+	| 'BATCH_TOO_LARGE'
 	| 'INTERNAL_ERROR';
 
 export interface BackendError {
@@ -139,6 +140,8 @@ export function getErrorMessage(code: ErrorCode | string | undefined): string {
 			return m.error_forbidden();
 		case 'VALIDATION_ERROR':
 			return m.error_validation_error();
+		case 'BATCH_TOO_LARGE':
+			return m.error_batch_too_large();
 		default:
 			return m.error_internal_error();
 	}