Upgrade Dockerfile to support Observium 24.12

[spoulson]

• Update amd64 Dockerfile.
  • Run on latest Ubuntu 24.04 image.
  • Supports running latest Observium 24.12.
• Update docker-compose.yml for recommended best practices.
• Update README.md with build image instructions.

[spoulson]

@somsakc Please note that I did not update for arm32v7 architecture because I don't have necessary tooling ready to go to build and test. Feel free to add to this MR.

[somsakc]

Thanks for your comments, I will merge all of them soonest.

For arm32v7 architect, it can be built, e.g. using "docker buildx" tool for multiple platforms (running on general computer as well). BTW, my raspi box is v2 and too slow for testing. So, I am in the middle to push on the old box or moving forward to newer arm64/v8 instead. At this situation, I keep the arm32v7 code unchanged due to no testing.