(Extension) Earn flow #2891

• Fixed Pool only

Design
Figma link here

UPDATE: when we first implemented this (more than 2 months ago) we were still Freighter and had only dark mode, so this task now is about rebasing the open PR to Varial with dark+light mode, review and adjust designs, wrap-up things, get PR reviewing, then merge.

We're going to use Blend 2.1 now, not 2.0. There is a new fixed pool for 2.1.

I will also need to get our backend up-to-date with this since our blend branches are too old now.