You’re nailing your goal then!
I would still steer you slightly towards documenting your architectural decisions more. It's a good skill to have and will help you in a long run.
You have dozens of crate dependencies and only you know why they are in there. A high-level document on how your system interconnects and how the algorithms under the hood work will be a huge help to anyone who comes looking through your source code. We become better programmers not by reading the source code, but by understanding what it actually does.
Here's a random trivia: your server depends on trust-dns-resolver. Why? Why wasn’t the stock resolver enough? Is that a design choice or you just wanted to have fun? There is no wrong answer but without the design notes it's hard to figure your intent.
That's a good point. Mind that in most production environments you'd be firewalled rather hard (especailly when it comes to logs processing which oftentimes ends up having PII). I wouldn’t trust any service that tries to use DoT or DoH in there that I couldn’t snoop on. Many deployments nowadays allow you to "punch" firewall holes based on the outgoing dns requests to an allowlisted domain, so chances are you actually want to use the glibc resolver and not try to be fancy.
That said, smaller images are always good in my book!