Store events and create deliveries in the delivery engine (closes #544)

The receiver, resubmit and replay handlers now read and check the
request and make one call. Engine.StoreEvent stores an event with a
pending delivery for each active target and the totals in one
transaction, then queues them; Engine.CreateReplay does the same for
one replay delivery. The handlers take *delivery.Engine, so the
Notifier interface and its bridge are gone, and the engine's notify is
no longer exported. Archives and CircuitBreakers stay because the
handler tests fake them. The tests that read a queued task moved to
the engine's tests; the handler tests use an engine that is never
started.

Model: opus-5-5

internal/resetpw/resetpw_test.go

@@ -131,10 +131,6 @@ func run(
 	return code, stdout.String(), stderr.String()
 }
 
-type noopNotifier struct{}
-
-func (n *noopNotifier) Notify([]delivery.Task) {}
-
 type noopArchives struct {
 	renameMu sync.Mutex
 }
@@ -190,7 +186,12 @@ func newServerApp(
 			database.NewWebhookDBManager,
 			healthcheck.New,
 			session.New,
-			func() delivery.Notifier { return &noopNotifier{} },
+			archive.NewWriters,
+			// The engine is built on a lifecycle that is never started,
+			// so no worker runs.
+			func(p delivery.EngineParams) *delivery.Engine {
+				return delivery.New(fxtest.NewLifecycle(t), p)
+			},
 			func() archive.Archives { return &noopArchives{} },
 			func() delivery.CircuitBreakers {
 				return &noopCircuitBreakers{}