add dockerfile for backend flask server

Author: GREENRAT-K405

server/Dockerfile

@@ -0,0 +1,14 @@
+FROM python:3.9.6-slim
+
+ENV PORT=8000
+
+WORKDIR /app
+
+COPY requirements.txt .
+
+RUN pip install --no-cache-dir -r requirements.txt
+COPY . .
+
+EXPOSE 8000
+
+CMD ["sh", "-c", "gunicorn --bind 0.0.0.0:${PORT} server:app"]