Issue 810 ipv4 detection

[jelveh]

Node.js 18+ changed the os.networkInterfaces() API to return numeric family values (4, 6) instead of strings ('IPv4', 'IPv6'). This caused the server startup message to not display any available network addresses on newer Node versions.

This PR updates the interface filtering logic to handle both string and numeric family formats, ensuring compatibility across all Node.js versions.

Changes:

• Modified IPv4 interface detection to accept both 'IPv4' and 4 as valid family values
• Added tests covering both string and numeric family formats
• Added test coverage for IPv6 link-local address filtering

Relevant issues

Fixes #810

Contributor checklist

• Provide tests for the changes (unless documentation-only)
• Documented any new features, CLI switches, etc. (if applicable)
  • Server --help output
  • README.md
  • doc/http-server.1 (use the same format as other entries)
• The pull request is being made against the master branch

[jelveh]

A contribution was made 3 years ago (#811) aiming to fix this issue. Since the PR was not merged in the time being, based on experience, it is very difficult to revive it (contributors move on, context is lost, ...). So I decided to submit a new PR that fixes this issue and close the old one.