chore(deps): bump Alpine 3.21→3.22, update CI actions and linter

- Dockerfile: alpine 3.21 → 3.22 (fewer CVEs per Docker Scout)
- release.yml: actions/checkout v4→v6, setup-go v5→v6, setup-buildx v3→v4
- ci.yml: golangci-lint v2.11.3 → v2.11.4
- DOCKERHUB.md: update Alpine version reference

.github/workflows/ci.yml

@@ -62,7 +62,7 @@ jobs:
       - name: Run golangci-lint
         uses: golangci/golangci-lint-action@v9
         with:
-          version: v2.11.3
+          version: v2.11.4
 
   coverage:
     name: Coverage