- Add `contract.go` to manage and validate embedded SQL migrations
- Introduce `AssertSchema` to verify database version at startup
- Include `SchemaMismatchError` with actionable recovery instructions
- Add comprehensive unit tests for version parsing and validation
- implement `nodes`, `rollout`, `ssh`, and `status` commands
- add `migrate-conf` utility to register existing nodes with the gateway
- update database schema to support operator wallet tracking for nodes