Harden OTLP exporter transport and auth warning handling

[manas-fortifyroot]

Summary

This PR hardens FortifyRoot/OpenLLMetry OTLP exporter endpoint handling for traces, metrics, and logs.

Changes include:

• Reject plaintext grpc:// exporters unless the target is localhost or loopback.
• Treat bare host:port gRPC endpoints as secure by default.
• Reject plaintext http:// exporters for non-local endpoints.
• Reject endpoint URLs that include username/password userinfo.
• Remove host.docker.internal from the local plaintext allowlist.
• Make auth-warning endpoint labels strip userinfo defensively.
• Handle invalid endpoint ports safely in auth-warning labels.
• Add IPv6 loopback and endpoint-label regression coverage.

Security Notes

This reduces accidental plaintext telemetry export and prevents credentials embedded in endpoint URLs from appearing in exporter targets or warning logs.

Validation

• ./scripts/run-tests.sh --package traceloop-sdk -- -q tests/test_sdk_initialization.py tests/test_fortifyroot_auth_warnings.py
• ./scripts/run-tests.sh --all
• python3 scripts/apply-fr-modification-notices.py --check