add docker files

backend/.dockerignore

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+.dockerignore
+Dockerfile

backend/Dockerfile

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+FROM python:3.13-alpine
+WORKDIR /app
+COPY requirements.txt .
+COPY . .
+RUN pip install --no-cache-dir -r requirements.txt
+EXPOSE 8000
+CMD ["gunicorn", "--bind", "0.0.0.0:8000", "base.wsgi:application"]