Incorporate Demo functionality into main branch

[obrusvit]

Design: Figma

Continuation of #4131, where the Demo flows were created for TS3 and TS5. Description on Notion.

It would make sense to incorporate the demo functionality into the main branch. The demo functionality is useful for showcasing and marketing purposes. Having a standard way of doing it outweighs the cost of rebasing the demo branch to main and also implicitly prepares it for future products.

• find out how to gate the feature for production build, ideas:
  • separate build target
  • conditional in command line
• add UI tests