feat(video-generation): update status in UI via websocket

[robinboehm]

Track current state of the image-, audio- and video-generation via websocket in the web-ui.

let exampleTypes = `
     NEEDS_UPDATE -> UPDATING -> UP_TO_DATE
  `;

let exampleState = {
  lesson_id: 123,
  video_state: "NEEDS_UPDATE",
  slides: [
    {
      slide_id: 123,
      video_state: "UP_TO_DATE",
      audio_state: "UP_TO_DATE",
      image_state: "UP_TO_DATE",
    }
  ]
}

• Video Module should return a stream that updates on every generation
• Connect Stream to lesson_controller/generate_video and push to socket
• Add processing icons to view layer

[sbrink]

Please create two versions:

• lesson only
• lesson + slides