chore(deps): Bump alpine from 3.18 to 3.21 in /alpine

Bumps alpine from 3.18 to 3.21.

---
updated-dependencies:
- dependency-name: alpine
  dependency-version: '3.21'
  dependency-type: direct:production
  update-type: version-update:semver-minor
...

Signed-off-by: dependabot[bot] <[email protected]>

Author: dependabot[bot]

alpine/Dockerfile

@@ -1,12 +1,12 @@
 # Etapa 1: Construção
-FROM alpine:3.18@sha256:de0eb0b3f2a47ba1eb89389859a9bd88b28e82f5826b6969ad604979713c2d4f AS builder
+FROM alpine:3.21@sha256:a8560b36e8b8210634f77d9f7f9efd7ffa463e380b75e2e74aff4511df3ef88c AS builder
 
 RUN apk update && apk add --no-cache nginx
 
 COPY index.html /var/www/html/
 
 # Etapa 2: Imagem final
-FROM alpine:3.18@sha256:de0eb0b3f2a47ba1eb89389859a9bd88b28e82f5826b6969ad604979713c2d4f
+FROM alpine:3.21@sha256:a8560b36e8b8210634f77d9f7f9efd7ffa463e380b75e2e74aff4511df3ef88c
 
 COPY --from=builder /etc/nginx /etc/nginx
 COPY --from=builder /usr/sbin/nginx /usr/sbin/nginx