fix: backend-py/Dockerfile to reduce vulnerabilities

The following vulnerabilities are fixed with an upgrade:
- https://snyk.io/vuln/SNYK-DEBIAN11-DB53-2825168
- https://snyk.io/vuln/SNYK-DEBIAN11-GLIBC-521063
- https://snyk.io/vuln/SNYK-DEBIAN11-GLIBC-521063
- https://snyk.io/vuln/SNYK-DEBIAN11-SQLITE3-6139925
- https://snyk.io/vuln/SNYK-DEBIAN11-ZLIB-6008961

backend-py/Dockerfile

@@ -12,7 +12,7 @@ RUN pip install poetry==1.6.1 && \
     poetry install --no-root -vvv --without dev --sync
 
 # Deploy
-FROM python:slim-bullseye AS deploy
+FROM python:3.13.0a2-slim AS deploy
 
 # Output to stdout/stderr, don't create .pyc files, etc.
 ENV PYTHONUNBUFFERED=1 \