Non-priority embedded wallet snags

[JonRay15]

The Chore

Follow up work deprioritised from first batch.

Tasks

• [ ] Modals are full screen and not contained to the wallet, which is weird.
• [ ] TX queue not behaving
• [ ] Possible perf issues in mobile
• [ ] No path to persistence of the wallet
• [ ] We don't remember if you had a wallet before. This could cause mild heart attacks for less techy users; "why do I need to do this again?", "are my funds lost?" Can we store a map of keys you've connected with before so we can show a slightly more customised message?

Additional details / background info