chore: Remove RunSpan in favor of defer style spans

[shiroyasha]

Two reasons:

1/ Cosmetically: The RunSpan was dirtying up the call site
2/ Controllable error: The RunSpan was handling the error no matter what, even if we don't want to report it.

[superplanehq-integration]

👋 Commands for maintainers:

• /sp start - Start an ephemeral machine (takes ~30s)
• /sp stop - Stop a running machine (auto-executed on pr close)

[shiroyasha]

I hate this:

But, that is a job for another PR.

[superplane-gh-integration-9000]

Risk: 15/100 (very low)

Summary

Replaces the RunSpan callback pattern with a defer-based Span helper across 17 files, adds gorm.ErrRecordNotFound suppression, and includes new unit tests.

Concerns

• telemetry package now imports gorm.io/gorm, coupling observability to the ORM layer.
• serializeCanvasVersions and serializeAdminOrganizations declare var err error never assigned; span errors will never be recorded.
• listAllOrganizations passes ctx to the span but does not thread ctx into models.ListAllOrganizations; DB queries won't be traced under that span.
• loadRootEventsForRunsSpan is a thin single-use wrapper with an inconsistent naming convention vs. other helpers.

Recommended reviewers: forestileao, lucaspin