feat: add BillingSyncWorker to dev Oban cron schedule

- Enables daily billing sync at 3 AM UTC in development
- Matches production configuration for testing
- All 54 billing tests passing

config/dev.exs

@@ -94,7 +94,9 @@ config :towerops, Oban,
        # System insights (agent offline detection) every 5 minutes
        {"*/5 * * * *", Towerops.Workers.SystemInsightWorker},
        # Gaiia reconciliation insights nightly at 4:30 AM
-       {"30 4 * * *", Towerops.Workers.GaiiaInsightWorker}
+       {"30 4 * * *", Towerops.Workers.GaiiaInsightWorker},
+       # Sync device usage to Stripe daily at 3 AM UTC
+       {"0 3 * * *", Towerops.Workers.BillingSyncWorker}
      ]},
     # Automatically delete completed jobs after 60 seconds
     {Oban.Plugins.Pruner, max_age: 60},