Transitioned from obsolete gateway object classes (`edge_gateway_shell_action_jobs_o`, `edge_gateway_shell_events_o`, `edge_gateway_shell_sessions_o`, `edge_gateway_update_jobs_o`) to the new agent implementation (`edge-gateway-agent/agent.php`).
This commit introduces delivery metadata tracking for gateway commands, updates, and shells. Adds preferred delivery channel handling, refined validation for edge agents, improved relay management logic, and broker presence reporting. Includes schema changes, enhanced shell handling, and test coverage.
Refactored the edge agent to include robust update handling, verification, and rollback procedures. Enhanced test coverage for critical update flows and introduced support for background edge gateway refresh without disrupting current user actions.