fix(entrypoint): skip bw config server while logged in

[TaprootFreak]

Summary

• The bw CLI refuses config server <url> while logged in: error Logout required before server config update
• After PR feat(monitoringV2): minter-guard auto-deny watcher #33 deployed, both jdt-monitoring and jdm-monitoring on dfxdev crash-loop on entrypoint with that error (host's copied bw data is already logged in)
• This PR replaces the setter call with a getter that just verifies the URL matches; if it doesn't match we exit fast with a clear error

Test plan

• dfxdev containers start successfully after deploy (no crash-loop)
• MinterGuard ENABLED log line appears once the vault items exist

[TaprootFreak]

Superseded by #39, which removes the bw integration entirely in favor of the standard .env pattern.