fix(build): Avoid Docker Hub pull throttling by using public ECR registry

[khvn26]

Thanks for submitting a PR! Please check the boxes below:

• I have run pre-commit to check linting
• I have added information to docs/ if required so people know about the feature!
• I have filled in the "Changes" section below?
• I have filled in the "How did you test this code" section below?
• I have used a Conventional Commit title for this Pull Request

Changes

This swaps out base images from Docker Hub to ones from Public ECR. This helps to avoid Docker Hub throttling on ARM64 runners (see actions/runner-images#1445 (comment)).

How did you test this code?

Pulled each of the new images and made sure they're identical to the ones from Docker Hub.

[vercel]

The latest updates on your projects. Learn more about Vercel for Git ↗︎

3 Skipped Deployments

Name	Status	Preview	Comments	Updated (UTC)
docs	⬜️ Ignored (Inspect)			Jul 8, 2024 1:29pm
flagsmith-frontend-preview	⬜️ Ignored (Inspect)			Jul 8, 2024 1:29pm
flagsmith-frontend-staging	⬜️ Ignored (Inspect)			Jul 8, 2024 1:29pm

[github-actions]

flagsmith-frontend image build and security scan finished ✨

Image	Build Status	Security report
ghcr.io/flagsmith/flagsmith-frontend:pr-4292	Finished ✅	Results ✅

[github-actions]

flagsmith image build and security scan finished ✨

Image	Build Status	Security report
ghcr.io/flagsmith/flagsmith:pr-4292	Finished ✅	Results ✅

[github-actions]

flagsmith-api image build and security scan finished ✨

Image	Build Status	Security report
ghcr.io/flagsmith/flagsmith-api:pr-4292	Finished ✅	Results ✅

[github-actions]

flagsmith-private-cloud image build and security scan finished ✨

Image	Build Status	Security report
ghcr.io/flagsmith/flagsmith-private-cloud:pr-4292	Finished ✅	Results ✅

[github-actions]

flagsmith-e2e image build finished ✨

Image	Build Status	Security report
ghcr.io/flagsmith/flagsmith-e2e:pr-4292	Finished ✅	Skipped

[github-actions]

Uffizzi Preview deployment-53944 was deleted.