Fix Link header processing to only parse ICE servers

[recursivecodes]

Description

• Add rel="ice-server" validation in extract_ice_info() to prevent processing control endpoint URLs as STUN servers
• Skip non-ICE server Link headers (playback-controls, session-delete, etc.)
• Add proper logging for ICE server discovery and fallback behavior
• Prevent memory corruption from storing control endpoints as STUN URLs
• Maintain backward compatibility with user-configured ICE servers

Fixes issue where WHIP servers sending multiple Link headers would cause the first header (typically a control endpoint) to be incorrectly parsed as an ICE server, leading to connection failures.

Related

Fixes issue from #77.

Testing

Confirmed to fix the issue mentioned in #77.

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Checklist

Before submitting a Pull Request, please ensure the following:

• 🚨 This PR does not introduce breaking changes.
• All CI checks (GH Actions) pass.
• Documentation is updated as needed.
• Tests are updated or added as necessary.
• Code is well-commented, especially in complex areas.
• Git history is clean — commits are squashed to the minimum necessary.

[TempoTian]

Thanks for your great effort. We can only merge code from internal server. So I commited it in a1c59f6. You can try to use latest version.

[recursivecodes]

Thanks @TempoTian - can we close this PR then?

[TempoTian]

Yes, if new version works OK, you can cancel it.