Fix: install postgresql-client so dbshell works in buffalogs container

[nishantxscooby]

Problem

Running python manage.py dbshell inside the buffalogs Django container fails with:

CommandError: You appear not to have the 'psql' program installed or on your path.

This makes it impossible to inspect the database from inside the container.

Steps to Reproduce

1. Run the stack with:

   docker compose up -d

2. Enter the Django container:

   docker compose exec buffalogs bash
   python manage.py dbshell

3. Observe the error above.

Fix

Added postgresql-client to the apt dependencies in build/Dockerfile so the psql binary is available inside the Django container.

Verification

After rebuilding the image:

docker compose exec buffalogs bash
command -v psql
python manage.py dbshell

dbshell now opens correctly.

[nishantxscooby]

Hi maintainers,
this PR fixes the missing psql binary in the Django container so manage.py dbshell works correctly.
Happy to make any changes if needed. Thanks for the review!

[Lorygold]

One consideration: postgresql-client is only needed for development/debugging and not for the application at runtime.

Would it make sense to query the database directly from the Postgres container (> docker compose exec postgres psql -U user dbname) instead of adding this dependency to the buffalogs application container?