Update EOC/IM Scheduling Process Documentation and Configuration

Problem

Current handbook documentation and terraform configurations for EOC/IM scheduling reference PagerDuty. These need to be updated for incident.io.

Tasks

1. Update handbook:
   • EOC scheduling process
   • IM scheduling process
   • On-call handover procedures
   • Any PagerDuty-specific instructions
2. Update config-mgmt (terraform):
   • Remove PagerDuty provider, we will manage the schedules via UI for now
   • We should create some sort of audit log / process for making changes though

Acceptance Criteria

• Handbook MRs created for all on-call process updates
• PD Terraform configurations removed (or MRs ready to go for cutover)
• Process documentation reviewed by EOC/IM leads