Fix dev server rejecting non-localhost hosts when using FX_PROFILER_HOST

[ojuschugh1]

This PR fixes #5865

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 85.42%. Comparing base (23fea36) to head (5cb9f6e).
⚠️ Report is 7 commits behind head on main.

Additional details and impacted files

@@           Coverage Diff           @@
##             main    #5889   +/-   ##
=======================================
  Coverage   85.42%   85.42%           
=======================================
  Files         321      321           
  Lines       32073    32073           
  Branches     8821     8823    +2     
=======================================
  Hits        27398    27398           
  Misses       4244     4244           
  Partials      431      431           

☔ View full report in Codecov by Sentry.
📢 Have feedback on the report? Share it here.

🚀 New features to boost your workflow:

• ❄️ Test Analytics: Detect flaky tests, report on failures, and find test suite problems.
• 📦 JS Bundle Analysis: Save yourself from yourself by tracking and limiting bundle sizes in JS merges.

[mstange]

Thanks! Some small comments but overall looks good.

[fatadel]

Hey @ojuschugh1,

Thanks a lot for the PR! It looks overall good, however, going thru the "Steps to reproduce" of the original issue still leads to the same error for me. Could you please have another look?

[ojuschugh1]

Hey @fatadel, good catch - the original fix only handled the proxy's own host check but missed that esbuild itself started validating the Host header since v0.25.0. When accessing via a LAN IP, the proxy was forwarding the original Host header (e.g. 192.168.1.100:4242) to esbuild, which rejected it with a 403.

I've pushed a fix that rewrites the Host header to match esbuild's bound address before proxying. Also added IPv6 wildcard support to isHostAllowed. Could you try again with the latest changes?