feat: move to self-hosted runners

[TimLohrer]

No description provided.

[Copilot]

Pull Request Overview

This PR migrates GitHub Actions workflows from GitHub-hosted runners to self-hosted runners, along with a minor fix to the backend Dockerfile path.

• Updated workflow runners from ubuntu-latest to self-hosted
• Added a new test build workflow for push events
• Corrected file path in backend Dockerfile from data/ua_regex.yaml to static/ua_regex.yaml

Reviewed Changes

Copilot reviewed 3 out of 3 changed files in this pull request and generated 2 comments.

File	Description
backend/Dockerfile	Fixed file path for ua_regex.yaml from data/ to static/ directory
.github/workflows/on-push.yml	New workflow for testing builds on push/PR events using self-hosted runners
.github/workflows/docker-multi-image.yml	Changed runner from ubuntu-latest to self-hosted

---

_{Tip: Customize your code reviews with copilot-instructions.md. Create the file or learn how to get started.}