feat: update Dockerfile&add github action

[ryoppippi]

Hi!
I tried to build lightpanda's docker image, but because of recent changes in v8 I couldn't build it. Also I found that there is no ci on Dockerfile. In addition, this dockerfile doesn't use multi-stage build efficiency.
So this pr includes

• enhance multi-stage building
• add ci
• Automatic detection of cpu archtecture.

You can see the build result here

https://github.com/ryoppippi/browser/actions/runs/14534577660/job/40780436433

[github-actions]

Thank you for your submission, we really appreciate it. Like many open-source projects, we ask that you sign our Contributor License Agreement before we can accept your contribution. You can sign the CLA by just posting a Pull Request Comment same as the below format.

---

I have read the CLA Document and I hereby sign the CLA

---

_{You can retrigger this bot by commenting recheck in this Pull Request. Posted by the CLA Assistant Lite bot.}

[ryoppippi]

Separated the make commands because we can use build cache in each command.
We use multi-stage build so we don't have to worry about the final image size

[ryoppippi]

we need to fix Makefile later actually...
I copy-n-pasted it from build.yml

[ryoppippi]

If I need to change something, let me know! please write it down here!