Add Docker support with sigra container

Dockerfile

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+FROM python:3.13-slim
+
+WORKDIR /app
+
+RUN pip install --no-cache-dir flask==3.1.3 jinja2==3.1.6 werkzeug==3.1.6
+
+COPY . .
+
+ENV FLASK_APP=app.py
+ENV FLASK_RUN_HOST=0.0.0.0
+ENV FLASK_RUN_PORT=5000
+
+EXPOSE 5000
+
+CMD ["python", "app.py"]