Security: Prevent gateway credential exfiltration via URL override (#9179)

* Gateway: require explicit auth for url overrides

* Gateway: scope credential blocking to non-local URLs only

Address review feedback: the previous fix blocked credential fallback for
ALL URL overrides, which was overly strict and could break workflows that
use --url to switch between loopback/tailnet without passing credentials.

Now credential fallback is only blocked for non-local URLs (public IPs,
external hostnames). Local addresses (127.0.0.1, localhost, private IPs
like 192.168.x.x, 10.x.x.x, tailnet 100.x.x.x) still get credential
fallback as before.

This maintains the security fix (preventing credential exfiltration to
attacker-controlled URLs) while preserving backward compatibility for
legitimate local URL overrides.

* Security: require explicit credentials for gateway url overrides (#8113) (thanks @victormier)

* Gateway: reuse explicit auth helper for url overrides (#8113) (thanks @victormier)

* Tests: format gateway chat test (#8113) (thanks @victormier)

* Tests: require explicit auth for gateway url overrides (#8113) (thanks @victormier)

---------

Co-authored-by: Victor Mier <victormier@gmail.com>

CHANGELOG.md

@@ -29,6 +29,7 @@ Docs: https://docs.openclaw.ai
 - Web UI: resolve header logo path when `gateway.controlUi.basePath` is set. (#7178) Thanks @Yeom-JinHo.
 - Web UI: apply button styling to the new-messages indicator.
 - Security: keep untrusted channel metadata out of system prompts (Slack/Discord). Thanks @KonstantinMirin.
+- Security: require explicit credentials for gateway URL overrides to prevent credential leakage. (#8113) Thanks @victormier.
 - Voice call: harden webhook verification with host allowlists/proxy trust and keep ngrok loopback bypass.
 - Cron: accept epoch timestamps and 0ms durations in CLI `--at` parsing.
 - Cron: reload store data when the store file is recreated or mtime changes.