fix: URL validation for hostnames with ports (no protocol)

[mbtools]

Fixes a bug in isURL where URLs like localhost:3000 and service-name:8080 were incorrectly rejected whenrequire_protocol was set to false. The validator was misinterpreting the colon in hostname:port patterns as a protocol delimiter.

I added tests to cover this case and a couple other option variations.

Regression #2608
Closes #2620

Checklist

• PR contains only changes related; no stray files, etc.
• README updated (where applicable)
• Tests written (where applicable)
• References provided in PR (where applicable)

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 100.00%. Comparing base (4af6124) to head (430cd2a).
⚠️ Report is 1 commits behind head on master.

Additional details and impacted files

@@            Coverage Diff            @@
##            master     #2622   +/-   ##
=========================================
  Coverage   100.00%   100.00%           
=========================================
  Files          114       114           
  Lines         2562      2566    +4     
  Branches       649       651    +2     
=========================================
+ Hits          2562      2566    +4     

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