fix(httpserver): guard OnStop against nil srv when OnStart was never called

If a component earlier in the launcher sequence fails during OnInit or OnStart,
the launcher calls OnStop on every already-registered component for cleanup.
httpserver.OnStop previously called s.srv.Shutdown(ctx) unconditionally; because
s.srv is only assigned inside OnStart, any shutdown triggered before OnStart ran
caused a nil pointer panic.

Add an early return in OnStop: `if s.srv == nil { return nil }`.

httpserver.go

@@ -107,8 +107,12 @@ func (s *httpServer) OnStart() error {
 }
 
 // OnStop performs a graceful shutdown, waiting up to 10 seconds for in-flight
-// requests to complete.
+// requests to complete. If OnStart was never called (e.g. a prior component
+// failed during startup), this is a no-op.
 func (s *httpServer) OnStop() error {
+	if s.srv == nil {
+		return nil
+	}
 	s.logger.Info("httpserver: shutting down gracefully")
 	ctx, cancel := context.WithTimeout(context.Background(), 10*time.Second)
 	defer cancel()