test: wait for postgres readiness log twice (avoid connection-reset flake)

internal/testsupport/containers.go

@@ -33,7 +33,11 @@ func StartPostgres(ctx context.Context) (dsn string, terminate func(), err error
 		tcpostgres.WithUsername("artifacts"),
 		tcpostgres.WithPassword("artifacts123"),
 		testcontainers.WithWaitStrategy(
-			wait.ForListeningPort("5432/tcp").WithStartupTimeout(60*time.Second),
+			// Postgres opens the port, runs init scripts, then restarts, so wait
+			// for the readiness log to appear twice to avoid connection resets.
+			wait.ForLog("database system is ready to accept connections").
+				WithOccurrence(2).
+				WithStartupTimeout(60*time.Second),
 		),
 	)
 	if err != nil {