Fix: remove legacy psycopg2 dependency not required for default SQLite setup

[shamilsj2025aids]

What this PR does

Removes psycopg2 and its associated system dependencies from the project
as they are not required for the default SQLite database configuration.

Investigation

As investigated in issue #382, the default database in pygoat/settings.py
is SQLite (django.db.backends.sqlite3), not PostgreSQL. psycopg2 is a
PostgreSQL driver and serves no purpose in the default setup.

The apt-get line in the Dockerfile that installs libpq-dev, python3-dev,
and dnsutils exists solely to support psycopg2 — and is a direct
contributor to the EOL Debian Buster build failure.

Changes made

• Removed psycopg2==2.9.3 from requirements.txt
• Removed the apt-get install line and its comment from Dockerfile

Impact

• Fixes Docker build failure caused by EOL Debian Buster repositories
• Reduces image size and build complexity
• Removes an unused legacy Heroku deployment dependency

Closes #382

[Copilot]

Pull request overview

This PR aims to simplify the default SQLite-based setup by removing the legacy PostgreSQL driver (psycopg2) and related Docker system packages, while also improving the README intro text.

Changes:

• Removed psycopg2==2.9.3 from requirements.txt.
• Removed an apt-get install layer (including dnsutils, libpq-dev, python3-dev) from the Dockerfile.
• Rewrote the README opening description for clarity.

Reviewed changes

Copilot reviewed 2 out of 3 changed files in this pull request and generated no comments.

File	Description
requirements.txt	Drops the Postgres driver dependency.
Dockerfile	Removes OS package installation previously used for runtime tooling and Postgres build deps.
README.md	Updates the project’s introductory description.

Comments suppressed due to low confidence (1)

Dockerfile:12

• This change removes installation of dnsutils, but the app executes dig/nslookup in the command-injection lab (cmd_lab). The Docker image should explicitly include those binaries (or the lab should be refactored not to depend on them), otherwise that functionality will break in containerized runs.

# set work directory
WORKDIR /app




# Set environment variables
ENV PYTHONDONTWRITEBYTECODE=1
ENV PYTHONUNBUFFERED=1

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