Enhance Docker Compose setup with network and minor stability improvements

[Sreeju7733]

This PR updates the docker-compose.yml file to improve structure, readability, and container communication.

• Added version: "3.9" for better Compose compatibility.
• Introduced a shared custom network (horilla-net) to improve service isolation and scalability.
• Quoted port mappings for consistency and safer YAML parsing.
• Updated healthcheck to use CMD-SHELL for improved reliability inside containers.

These changes enhance maintainability, make future service extensions simpler (e.g., adding Redis or Adminer), and slightly improve reliability when starting containers.

[hhc97]

https://docs.docker.com/reference/compose-file/version-and-name/

According to the docker docs the version top-level element is obsolete and should not be added moving forward.

[Sreeju7733]

Appreciate the reference to the docs!
I’ll make sure future contributions follow the new Compose spec without the version field.

[horilla-opensource]

Hi @Sreeju7733 ,

Thanks for the improvements here—quoting the port mappings, adding an explicit network, and the updated healthcheck all look good.

One change needed before merge: please remove the top-level version: "3.9" entry, since the version field is obsolete in modern Docker Compose.

Once version: is removed, this should be good to merge.

With Regards,
Team Horilla

[Sreeju7733]

I have updated the code, now it's ready to merge.