v0.19.4

• Fix: the snapshot only reached Android, not iOS. The two platforms expect the image in
  different places — Android reads data.image, iOS reads data.attachment.url. Only the
  Android field was set, so iPhone users got the name without a picture. Both are sent now;
  each platform ignores the other's field.
• When no Frigate URL is configured, neither field is emitted at all. An empty attachment
  makes the notification fail outright on iOS, so leaving the key out matters more than it
  looks.