fix: create app directory before writing start.sh in Dockerfile

Dockerfile

@@ -10,6 +10,7 @@ RUN apt-get update && \
 
 # Install Flask and set up the entry point
 RUN pip3 install flask && \
+    mkdir -p /home/user/app && \
     echo "flask run --host=0.0.0.0 --port=5000" > /home/user/app/start.sh && \
     chmod +x /home/user/app/start.sh