integrate fix-vendor-hash into ci.yml so we don't get redundant builds

[eljojo]

What this changes

unify CI actions for fixing nix hash and building docker image

How I tested this

built locally using nix

Checklist

• I have read CONTRIBUTING.md and this PR follows the guidelines
• A human has reviewed the entire diff of this PR, every line of code
• A human understands the changes and can explain why this approach is correct
• Tests pass (make full)
• This PR doesn't have AI-generated boilerplate or co-author lines
• This PR was authored and submitted by an AI agent without human review