Update Dockerfile with custom base image and add

healthcheck

- Update base image to `docker.io/library/alpine:3.18.4` to ensure the
latest version is used.
- Set the user in the container to `notatio` for security purposes.
- Add a healthcheck to monitor the app's availability.
- Modify the `ENTRYPOINT` to delay the execution by 10 seconds before
starting the application.

Dockerfile

@@ -14,7 +14,8 @@ COPY . ./
 RUN go build -o /notatio
 
 # Stage 2: Create the final image
-FROM alpine
+FROM docker.io/library/alpine:3.18.4
+USER notatio
 WORKDIR /
 
 COPY --from=builder /notatio .
@@ -25,5 +26,8 @@ COPY --from=builder /build/static/ static/
 COPY --from=builder /build/wait-for-postgres.sh ./wait-for-postgres.sh
 
 EXPOSE 9991
-CMD ["./notatio"]
+ENTRYPOINT ["sh", "-c", "sleep 10 && ./notatio"]
 LABEL name=notatio version=latest
+
+HEALTHCHECK --interval=5m --timeout=3s \
+  CMD curl -f http://localhost/ || exit 1