v0.7 trial cleanup: automate 90-day expired-tenant purge and verify FK-safe execution

[SheetMetalConnect]

Linear: ERY-17
Prior context: #605
Planning source: work/ERY-346-v0.7-execution-breakdown.md

Objective

• Ship the minimum operationally safe v0.7 cleanup path for expired trial tenants.

Scope

• Implement scheduled detection for expired trial tenants older than 90 days.
• Execute the purge in an FK-safe order with controlled audit-trigger behavior.
• Emit a non-secret cleanup record for operator visibility.
• Run one fixture-backed verification proving the purge path completes without the current deadlock failure mode.

Acceptance criteria

• Scheduled cleanup logic exists and is documented in code or task notes.
• Purge order and trigger handling are explicit and tested or otherwise verified.
• One verification artifact proves the cleanup succeeds against the known failure mode.