feat(gatekeeper): policies (#214)

* feat(infra): add edge rate limiting gateway and GlobalRateLimit CRD for POST /gists

* refactor: split events.rs into dedicated modules across contracts

* feat(k8s): add OPA Gatekeeper policy templates and constraints for no privileged, no latest, and require resource limits

* feat: add PrometheusRule CR for vertexchain alerts – migrate hand-rolled alert-rules.yml to K8s manifests

* fix(multisig): remove unused symbol_short import

* fix(contracts): remove unused symbol_short imports in governance and batch-wallet

* style(contracts): format soroban_sdk imports for rustfmt

* fix(contracts): update soroban-sdk and soroban-env-host dependencies to 22.1.3

* fix(contracts): pin soroban-sdk version to 22.0.11 in workspace dependencies

Author: ugoocreates-pixel