chore(docker): bump alpine from 3.21 to 3.23 (#5)

Bumps alpine from 3.21 to 3.23.

---
updated-dependencies:
- dependency-name: alpine
  dependency-version: '3.23'
  dependency-type: direct:production
  update-type: version-update:semver-minor
...

Dockerfile

@@ -17,7 +17,7 @@ RUN CGO_ENABLED=0 GOOS=${TARGETOS} GOARCH=${TARGETARCH} go build \
     ./cmd/api
 
 # Runtime stage — pure Alpine, no Node.js
-FROM alpine:3.21
+FROM alpine:3.23
 
 RUN apk --no-cache add ca-certificates wget && \
     adduser -D -H appuser