fix: Dockerfile to reduce vulnerabilities

The following vulnerabilities are fixed with an upgrade:
- https://snyk.io/vuln/SNYK-DEBIAN12-GLIBC-6210088
- https://snyk.io/vuln/SNYK-DEBIAN12-GLIBC-6210088
- https://snyk.io/vuln/SNYK-DEBIAN12-GLIBC-6210098
- https://snyk.io/vuln/SNYK-DEBIAN12-GLIBC-6210099
- https://snyk.io/vuln/SNYK-DEBIAN12-ZLIB-6008963

Dockerfile

@@ -1,6 +1,6 @@
 # syntax=docker/dockerfile:1
 # Prepare the base environment.
-FROM python:3.10.13-slim as builder_base_caddy
+FROM python:3.13.0a3-slim as builder_base_caddy
 MAINTAINER [email protected]
 LABEL org.opencontainers.image.source https://github.com/dbca-wa/caddy