Fix/backend ci postgres pnpm

[OmniZlatoon]

Summary

This PR addresses the backend CI failures from job 90823536503.

The workflow was failing due to:

• Postgres service connection issues, including logs showing:
  • "FATAL: role "root" does not exist"
• A pnpm lockfile parse error during dependency install.

What changed

• Removed the Postgres host port mapping from the GitHub Actions service definition to avoid host port collisions on runners.
• Updated the Postgres health check to target the configured user and database:
  • pg_isready -U soter -d soter_test
• Switched the workflow DATABASE_URL values from localhost to 127.0.0.1 so the service container is addressed correctly.
• Left the rest of the workflow unchanged.

Maintainer notes

If CI still fails because of a pnpm lockfile mismatch, regenerate the lockfile on a machine using Node 20 and pnpm 9:

corepack enable
corepack prepare pnpm@9 --activate
pnpm install --lockfile-only
pnpm install
pnpm --filter backend run build
pnpm --filter backend run test

closes #552

[OmniZlatoon]

Sir @Cedarich , I have opened another branch with the corrections. Please review and any further issues I am ready to solve

[Cedarich]

@OmniZlatoon

[OmniZlatoon]

I am working on it. its the pnpm-lock.yaml file that's causing the issue. I am pulling back from the main branch but the issue doesn't seem to go

[Cedarich]

@OmniZlatoon

[OmniZlatoon]

Good norning sir @Cedarich

[OmniZlatoon]

Good morning sir @Cedarich , I have pulled the recent pnpm-lock.yaml file from the main repo. Please verify the checks again.