fix: Dockerfile to reduce vulnerabilities

The following vulnerabilities are fixed with an upgrade:
- https://snyk.io/vuln/SNYK-DEBIAN12-ZLIB-6008963
- https://snyk.io/vuln/SNYK-DEBIAN12-SYSTEMD-5733390
- https://snyk.io/vuln/SNYK-DEBIAN12-SYSTEMD-5733398
- https://snyk.io/vuln/SNYK-DEBIAN12-TAR-1560620
- https://snyk.io/vuln/SNYK-DEBIAN12-UTILLINUX-2401083

Dockerfile

@@ -3,7 +3,7 @@ COPY requirements.txt .
 
 RUN pip install --user -r requirements.txt 
 
-FROM python:3.9-slim
+FROM python:3.13-slim
 WORKDIR /app
 COPY --from=builder /root/.local/* /app/.local/
 COPY chksftp.py .