feat(phase-5): on-prem sync poll hardening + stale job reclaim

Harden the Hub-side polling protocol for on-prem TapTrack agents:
- sync/poll: accept job_failed_ids (retry/fail on-prem delivery failures)
- sync/poll: deduct credits + write ledger when on-prem reports sent jobs
- sync/poll: return feature_flags (tier-based) + suspended flag in config
- sync/poll: skip job dispatch for suspended/expired schools
- sms_jobs: add delivered_via (pull|push) + processing_started_at columns
- tasks/sms: new sms.reclaim_stale_jobs task resets processing→pending if on-prem
  goes offline (jobs stuck >5 min), enabling Celery push fallback
- tasks/sms: tag Celery-sent jobs as delivered_via='push'
- worker: schedule reclaim_stale_jobs every 5 minutes
- migration: 001_phase5 adds delivered_via + processing_started_at to sms_jobs

.paul/ROADMAP.md

@@ -19,8 +19,8 @@ SMS flow: On-prem TapTrack polls Hub every 30s → Hub queues SMS jobs → Hub s
 ## Current Milestone
 
 **v1.0 — Foundation & Core Services**
-Status: Phase 4 complete — Phase 5 next
-Phases: 4 of 15 complete
+Status: Phase 5 complete — Phase 6 next
+Phases: 5 of 15 complete
 
 ---
 
@@ -32,7 +32,7 @@ Phases: 4 of 15 complete
 | 2     | School Registry + License Mgmt | 2   | ✅ Complete  | 2026-03-15 |
 | 3     | On-Prem License Validation     | 1   | ✅ Complete  | 2026-03-15 |
 | 4     | SMS Gateway (credits + queue)  | 2   | ✅ Complete  | 2026-03-15 |
-| 5     | On-Prem SMS Polling Agent      | TBD | Not started  | —          |
+| 5     | On-Prem SMS Polling Agent      | 1   | ✅ Complete  | 2026-03-16 |
 | 6     | Super Admin Dashboard UI       | TBD | Not started  | —          |
 | 7     | School Admin Portal UI         | TBD | Not started  | —          |
 | 8     | Billing Engine + Invoice PDF   | TBD | Not started  | —          |