Fixed Dockerfile

api/Dockerfile

 FROM python:3.9-alpine
 
-COPY . /app/
-WORKDIR /app
+COPY api.py /app/api.py
+COPY requirements.txt /app/requirements.txt
+COPY books.db /app/books.db
 
-RUN pip3 install -r requirements.txt
+RUN pip3 install -r /app/requirements.txt
 
 EXPOSE 5000
 
-ENTRYPOINT ["python3", "-u", "api.py"]
+ENTRYPOINT ["python3", "-u", "/app/api.py"]