trucking campaigns: daily builder + MX verifier concurrency + tracking column

- build_trucking_campaigns.py: nightly script that creates 8 Listmonk campaigns
  per day (4 TZ x 2 types: MCS-150 overdue 2k/TZ, inactive USDOT 1k/TZ)
  at 4AM ET / 5AM ET (CT) / 6AM ET (MT) / 7AM ET (PT). Deduplicates via
  listmonk_sent_at column.
- migration 083: add listmonk_sent_at + listmonk_campaign_type to fmcsa_carriers
- email_verifier.py: bump max_workers from 5 to 20 for 4x faster throughput
- cron: daily pw-trucking-campaigns at 08:00 UTC (3 AM EST)

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

infra/ansible/roles/worker-crons/defaults/main.yml

@@ -199,3 +199,12 @@ worker_crons:
     module: scripts.workers.quarterly_499q_notify
     on_calendar: "*-*-* 13:00:00 UTC"
     persistent: true
+
+  # Trucking campaign builder — 3 AM EST (08:00 UTC) daily.
+  # Creates 8 Listmonk campaigns for the next day's sends (4 TZ × MCS-150 + inactive USDOT).
+  # 2,000 carriers/TZ for MCS-150; 1,000 carriers/TZ for inactive USDOT.
+  - name: pw-trucking-campaigns
+    description: Build daily trucking Listmonk campaigns (MCS-150 overdue + inactive USDOT)
+    module: scripts.build_trucking_campaigns
+    on_calendar: "*-*-* 08:00:00 UTC"
+    persistent: true