chore(deps): update alpine docker tag to v3.21 (#279)

Co-authored-by: renovate[bot] <29139614+renovate[bot]@users.noreply.github.com>

backend-go/Dockerfile

@@ -12,7 +12,7 @@ RUN mkdir -p /workspace/app/target/application
 RUN CGO_ENABLED=0 GOOS=linux go build -v -o /workspace/app/target/application ./...
 HEALTHCHECK --interval=3000s --timeout=30s CMD go version || exit 1
 
-FROM alpine:3.20
+FROM alpine:3.21
 ARG DEPENDENCY=/workspace/app/target/application
 RUN apk add --no-cache bash
 RUN addgroup -S appgroup && adduser -S 1001 -G appgroup