feat(discovery-service): add docker image and ci workflow

[m-kus]

Add Docker support for Discovery Service

TL;DR

Adds Docker build configuration and GitHub Actions workflow for the Discovery Service component.

What changed?

• Created a multi-stage Dockerfile for the Discovery Service that builds a minimal Alpine-based image
• Added a GitHub Actions workflow to automatically build and publish Docker images to GitHub Container Registry
• Included comprehensive documentation for local and Docker builds, configuration options, and deployment instructions

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This change is 

[m-kus]

• feat(discovery-service): add optional tls termination #511
• feat(discovery): secret zeroization, request limits, error sanitization #510
• feat(discovery-service): add docker image and ci workflow #487 👈 (View in Graphite)
• main

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[idan-starkware]

@idan-starkware partially reviewed 3 files and all commit messages.
Reviewable status: complete! all files reviewed, all discussions resolved (waiting on Yoni-Starkware).

[idan-starkware]

Reviewable status: complete! all files reviewed, all discussions resolved (waiting on Yoni-Starkware).