[bernardom]

First, congratulations.

Second, let me focus on the management point. You wrote: "I managed an entire team of 10 people without ever missing a deadline of the whole team, and now they brought in an engineering manager"

a) Do you think the (now-bigger) team needs a full-time manager? b) If yes, did you want to become that full-time manager? c) If yes, did you make your desire known?

If the answer Yes, Yes, No, that's ok- lots of people want to continue being individual contributors. It's still on you to work with management to define the right structure that works for you and the company. Maybe you become some sort of Chief Architect. Maybe you help hire the manager.

Either way, if you were as pivotal as you say you were, you should certainly have the CEO's ear to bring this up in a constructive way.