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/plugins.ts

@@ -19,6 +19,7 @@ import * as smartnetwork from '@push.rocks/smartnetwork';
 import * as smartunique from '@push.rocks/smartunique';
 import * as smartstring from '@push.rocks/smartstring';
 import * as smarttime from '@push.rocks/smarttime';
+import * as taskbuffer from '@push.rocks/taskbuffer';
 
 export {
   lik,
@@ -30,6 +31,7 @@ export {
   smartunique,
   smartstring,
   smarttime,
+  taskbuffer,
 };
 
 // @tsclass scope