fix(backend): record turso errors on logfire spans
turso bad_gateway and http errors were only logged to stderr via
logfire.err(), not recorded on the otel spans. this made debugging
via logfire difficult since errors didn't show up as exceptions.
now calls span.recordError() + adds turso.status and turso.response
attributes so these errors are visible in logfire dashboard.
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Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>