text: Title: New key management hard-crashes on a bad key
  Body: Following on from #2994 discussions...
  
  The new key management is v0.8.1 is handy, but it hard crashes if it encounters a bad key:
  
  ```
  beat: Starting...
  2025-02-14 14:18:13 da9ef9a76ffe augur[7] INFO Retrieved 16 github api keys for use
  WARNING: The key 'redacted' is not a valid key. Hint: If valid in past it may have expired
  WARNING: The key 'redacted' is not a valid key. Hint: If valid in past it may have expired
  WARNING: The key 'redacted' is not a valid key. Hint: If valid in past it may have expired
  Protocol Error: <class 'httpx.ProtocolError'>
  
  augur backend start command setup failed
                   You are not connected to the internet.
                   Please connect to the internet to run Augur
                   Consider setting http_proxy variables for limited access installations.
  ```
  
  Given a long-lived instance is pretty much *guaranteed* to hit a bad or expired key during it's lifetime, this should be handled and reported to the user, rather than causing a crash. 