Performance Improvements

[zupzup]

This is a collection of several performance optimizations we already identified:

• With a lot of files on a bill (~100), the app gets very slow/sluggish (especially list of bill requests) - maybe related to switch identity
  • re-hydrating cache after switch identity
• Nostr initialization should be in parallel for multiple identities (companies and personals)
  • And it should be in the background (with offline functionality)

[zupzup]

Best-effort for 1.0.0 - as much as we can do

[zupzup]

Most importantly, initial startup should be sped up, by doing as much as possible in the background