Add Docker support with Gunicorn, SQLite volume persistence, and optional PostgreSQL

Co-authored-by: Cursor <cursoragent@cursor.com>

Dockerfile

@@ -0,0 +1,36 @@
+# FunZone Accounting Backend Dockerfile
+FROM python:3.11-slim
+
+ENV PYTHONDONTWRITEBYTECODE=1
+ENV PYTHONUNBUFFERED=1
+ENV DEBIAN_FRONTEND=noninteractive
+
+WORKDIR /app
+
+RUN apt-get update \
+    && apt-get install -y --no-install-recommends \
+        postgresql-client \
+        build-essential \
+        libpq-dev \
+        curl \
+    && rm -rf /var/lib/apt/lists/*
+
+COPY requirements.txt /app/
+RUN pip install --no-cache-dir -r requirements.txt
+
+COPY . /app/
+
+RUN mkdir -p /data \
+    && adduser --disabled-password --gecos '' appuser \
+    && chown -R appuser:appuser /app /data \
+    && chmod +x /app/docker-entrypoint.sh
+
+USER appuser
+
+EXPOSE 8010
+
+HEALTHCHECK --interval=30s --timeout=10s --start-period=30s --retries=3 \
+    CMD curl -f http://localhost:8010/health || exit 1
+
+ENTRYPOINT ["/app/docker-entrypoint.sh"]
+CMD ["gunicorn", "config.wsgi:application", "--bind", "0.0.0.0:8010", "--workers", "2", "--timeout", "120", "--access-logfile", "-", "--error-logfile", "-"]