Support multiple tokens

[chelmertz]

Personal + single work organization should be common, there are probably more patterns.

• associate each PR (or, by relations, the repository) with its access token's organization/user
• CRUD per token
• rethink passing tokens via env vars
  • possibly pass comma separated tokens, or do something in the GUI for it (and persist in sqlite)
• the refresh-loop should be associated with tokens, when restarting with a different token, we should throw away the last-queried