Update authorization header and add user agent

[MichaelZhang-Navex]

Hello dear maintainers, I installed it following the instructions and see the OTLP export failed error. I diged into it and found that the header of post request to logfire trace api should be in this way somehow.

[petyosi]

Sorry for the slow review here, and thank you for digging into the export failure.

After looking through the change, the User-Agent addition looks harmless to me, but I am hesitant about removing the Bearer prefix from the Authorization header in this code path. This script constructs the raw HTTP request itself, and the direct Logfire examples I found still use Authorization: Bearer ...

Could you share a bit more detail on how you reproduced the problem?

1. What exact error did you see from Logfire (HTTP status, response body, or stderr output)?
2. Which Logfire endpoint or region were you sending to?
3. Did the request still fail if you kept Authorization: Bearer and only added the User-Agent header?
4. If you have a minimal repro (curl, request dump, or a sanitized request and response snippet), that would help a lot.

That would make it much easier to separate a header-format issue from something else in the request.