feat(smartacme): Integrate @push.rocks/taskbuffer TaskManager to coordinate ACME certificate issuance with per-domain mutex, global concurrency cap, and account-level rate limiting; refactor issuance flow into a single reusable cert-issuance task, expose issuance events, and update lifecycle to start/stop the TaskManager. Add configuration for concurrent issuances and sliding-window order limits, export taskbuffer types/plugins, and update tests and docs accordingly.

ts/index.ts

@@ -9,3 +9,6 @@ export { certmanagers };
 // handlers
 import * as handlers from './handlers/index.js';
 export { handlers };
+
+// re-export taskbuffer event types for consumers
+export type { ITaskEvent, ITaskMetadata } from '@push.rocks/taskbuffer';