style(i18n): add missing newline at EOF in JSON files

- Ensures JSON files adhere to standard formatting by adding a newline
  at the end of the file.

src/i18n/de.json

@@ -19,4 +19,4 @@
     "hint_header": "\nℹ️  Hinweis:",
     "error_write_units": "Fehler beim Schreiben der Units:",
     "rollback_failed": "Rollback fehlgeschlagen:"
-}
+}

src/i18n/en.json

@@ -19,4 +19,4 @@
     "hint_header": "\nℹ️  Note:",
     "error_write_units": "Error while writing unit files:",
     "rollback_failed": "Rollback failed:"
-}
+}