fix: Minor fix to docker bake github actions

[creatorrr]

• feat: Add docker bake builder
• fix: Minor fix to agents-api/Dockerfile
• fix: Minor fix to docker bake github actions

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[!IMPORTANT] Introduce Docker Bake for image building, update Dockerfiles, and modify GitHub Actions workflows for Docker image management.

• GitHub Actions:
  • Add docker-bake-on-pr.yml for baking images on pull requests.
  • Rename dev-push-to-hub.yml to bake-push-to-hub.yml and main-push-to-hub.yml to latest-push-to-hub.yml.
  • Update bake-push-to-hub.yml and latest-push-to-hub.yml to use docker/bake-action@v5 and remove branch name and git sha setting steps.
• Dockerfiles:
  • Update agents-api/Dockerfile and related Dockerfiles to use poetry>=1.8.0,<1.9.0 and set PYTHONUNBUFFERED=1.
  • Add syntax and error check directives to Dockerfiles in agents-api, gateway, integrations-service, and memory-store.
  • Modify gateway/Dockerfile to include environment variable expectations and update entrypoint script.
• Configuration:
  • Add docker-bake.hcl to define build contexts and tags for Docker images.
• Documentation:
  • Update CONTRIBUTING.md with instructions for building Docker images using Docker Buildx Bake.

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