fix(i18n): replace raw translation keys on panel screens (#7057)

Use valid translation keys on six panel screens, add the missing copy-failure and empty-value strings across all locales, and reject unresolved literal translation keys in the regression test.

frontend/src/pages/clients/ClientBulkAdjustModal.tsx

@@ -95,7 +95,7 @@ export default function ClientBulkAdjustModal({
       <Modal
         open={open}
         title={t('pages.clients.bulkAdjustTitle', { count })}
-        okText={t('apply')}
+        okText={t('confirm')}
         cancelText={t('cancel')}
         confirmLoading={submitting}
         onOk={handleOk}