fix: Dockerfile to reduce vulnerabilities

The following vulnerabilities are fixed with an upgrade:
- https://snyk.io/vuln/SNYK-ALPINE318-OPENSSL-8235200
- https://snyk.io/vuln/SNYK-ALPINE318-OPENSSL-8235200

Dockerfile

@@ -1,6 +1,6 @@
 # the following version can be overridden at image build time with --build-arg
 # renovate: datasource=github-releases depName=gohugoio/hugo
-ARG HUGO_VERSION=0.141.0
+ARG HUGO_VERSION=0.124.1
 
 # remove/comment the following line completely to compile vanilla Hugo:
 ARG HUGO_BUILD_TAGS=extended
@@ -47,7 +47,7 @@ RUN go install github.com/yaegashi/muslstack@latest && \
 
 # ---
 
-FROM alpine:3.18
+FROM alpine:3.21.0
 
 # renew global args from above & pin any dependency versions
 ARG HUGO_VERSION