Audit admin mutation coverage for audit_logs completeness

[Taleef7]

Context

docs/plan-CorvEd.md still lists audit log completeness as a TODO. The audit log page exists, but every admin/server mutation should be reviewed for consistent audit records.

Acceptance criteria

• Inventory all admin/server mutations that change payments, requests, roles, tutors, matches, schedules, sessions, subjects, and packages.
• Confirm each meaningful mutation writes an audit_logs entry with useful action, entity_type, entity_id, and details.
• Add missing audit entries where needed.
• Add tests or a documented audit matrix.

References

• docs/plan-CorvEd.md section 4.3
• Related closed issue: T12.3 basic admin audit log for changes (match reassignment, session edits) #80