smartproxy/readme.plan.md

## Plan: Centralize Certificate Renewal for all certificates

- [ ] Remove renewal logic from Port80Handler
  - Delete `startRenewalTimer()` and `checkForRenewals()` methods
  - Remove `renewThresholdDays` and `renewCheckIntervalHours` options from `IPort80HandlerOptions`
- [ ] Expose certificate status from Port80Handler
  - Ensure `getDomainCertificateStatus()` returns `{certObtained, expiryDate}` for each domain
- [ ] Add renewal settings to SmartProxy
  - Extend `port80HandlerConfig` to include `renewThresholdDays` and `renewCheckIntervalHours`
- [ ] Implement renewal scheduler in SmartProxy using taskbuffer
  - Add dependency on `@push.rocks/taskbuffer` and import `{ Task, TaskManager }` in `SmartProxy`
  - Add `performRenewals()` to iterate domains and trigger renewals where `daysRemaining <= renewThresholdDays`
  - Instantiate a `TaskManager` and define a `Task` that wraps `performRenewals()`
  - Use `taskManager.addAndScheduleTask(task, cronExpr)` to schedule renewals, building `cronExpr` from `renewCheckIntervalHours` (e.g. `0 0 */${renewCheckIntervalHours} * * *`)
  - Call `taskManager.start()` in `SmartProxy.start()`
- [ ] Clean shutdown handling
  - Call `taskManager.stop()` in `SmartProxy.stop()` alongside other cleanup
- [ ] Throttling and safety
  - Skip domains already in `obtainingInProgress`
  - Optionally batch or stagger renewal calls for large domain sets
- [ ] Tests
  - Unit test `performRenewals()`, mocking `getDomainCertificateStatus()` to simulate expiring certificates
  - Integration test using an in-memory `Port80Handler` to verify that scheduled renewals invoke `obtainCertificate()` correctly
- [ ] Documentation
  - Update `readme.plan.md` (this section)
  - Update `README.md` and code comments to document new renewal settings and workflow