test: implement reconciler unit tests

[dennisonbertram]

Skeleton tests exist in internal/reconciler/reconciler_test.go — all currently t.Skip. Implement using testutil.NewStateDB and testutil.MockDockerClient.

Tests to implement:

• TestReconciler_CircuitBreaker — simulate 5 crashes in 600s window, verify circuit_open=1 and circuit_retry_at is set
• TestReconciler_AutoRecovery — set circuit_retry_at to past, run tick, verify circuit reset and status=stopped
• TestReconciler_UnhealthyRestart — mock InspectContainer returning HealthStatus="unhealthy", verify StopContainer called
• TestReconciler_StaleDeployment — service with status=deploying and updated_at >10min, verify marked failed

Depends on: #test-wire-migrations (testutil must use real migration runner)