fix(servers): show a friendly error when cache-alert resolve fails

[RonenMars]

Summary

• Catch failed cache-alert resolve (prune / ignore / reset) instead of leaving an uncaught NetworkError.
• Keep the sheet open and show a plain retry message so the user can try again.

Test plan

• Open a cache-alert sheet and confirm a successful prune still resolves as before.
• Force a failed resolve (unreachable server or 502) and confirm the red LogBox does not appear.
• Confirm the sheet stays open with: "Couldn't complete that action. Check the connection to this server and try again."
• Tap Proceed again after a failure and confirm the error clears while the request is in flight.