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/release.yml

@@ -12,11 +12,11 @@ jobs:
   release:
     runs-on: ubuntu-latest
     steps:
-      - uses: actions/checkout@v4
+      - uses: actions/checkout@v6
         with:
           fetch-depth: 0
 
-      - uses: actions/setup-go@v5
+      - uses: actions/setup-go@v6
         with:
           go-version-file: go.mod
 
@@ -32,7 +32,7 @@ jobs:
     needs: release
     runs-on: ubuntu-latest
     steps:
-      - uses: actions/checkout@v4
+      - uses: actions/checkout@v6
 
       - name: Docker meta
         id: meta
@@ -45,7 +45,7 @@ jobs:
             type=raw,value=latest
 
       - uses: docker/setup-qemu-action@v4
-      - uses: docker/setup-buildx-action@v3
+      - uses: docker/setup-buildx-action@v4
 
       - uses: docker/login-action@v4
         with: