Fix bare IPv6 host matching in config

[ryanfowler]

Summary

• Normalize bare URLs with bracketed IPv6 authorities before host matching so config host sections use the same host form as Url::host_str().
• Treat [::1]:3000/path as host ::1 instead of splitting on the first colon.
• Add a config regression test covering a [::1] host section applied to a bare IPv6 URL.

Testing

• cargo fmt
• cargo clippy --locked --all-targets --all-features -- -D warnings
• Added a focused unit test for the IPv6 host-matching regression.