Discard fx's own log in tests that build an fx app (closes #230)

fxtest.New sends fx's event log to t.Logf. When a start or stop runs
past fx's time limit, Start or Stop returns while the hook keeps
running in a goroutine, and that goroutine logs to the test after the
test has returned, which the race detector reports. Every fxtest.New
now passes fx.NopLogger, so nothing fx runs can reach the test. The
fxtest.Lifecycle sites are unchanged: they run hooks on the goroutine
that calls Start or Stop, which is always the test or its cleanup.

Model: opus-5-5

internal/handlers/handlers_test.go

@@ -86,6 +86,10 @@ func newTestApp(
 
 	return fxtest.New(
 		t,
+		// fx's own log is discarded, not sent to t.Logf: a hook still
+		// running after a start or stop timeout would write there after
+		// the test has returned.
+		fx.NopLogger,
 		fx.Provide(
 			globals.New,
 			logger.New,