docs(events): update event-based trigger docs and add auth events

[dragon3]

Summary

• Expand event data access documentation with args.eventType for all event types and add IdP/Auth event sections
• Add auth.access_token.issued event to the supported events page
• Remove outdated Properties table (was describing Terraform fields, not SDK)
• Clean up event data fields (e.g., clarify newRecord/oldRecord availability)