ci: replace Blacksmith actions with standard docker/* equivalents

Blacksmith's sticky disk cache (4.42 GB at $0.50/GiB/mo) costs more
than the marginal build-time savings it provides. The standard
docker/setup-buildx-action@v4 and docker/build-push-action@v7 are
already fast enough for our workload.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

Author: pan93412

.github/workflows/release.yml

@@ -30,10 +30,10 @@ jobs:
         uses: actions/checkout@de0fac2e4500dabe0009e67214ff5f5447ce83dd # v6.0.2
 
       - name: Set up Docker Buildx
-        uses: useblacksmith/setup-docker-builder@722e97d12b1d06a961800dd6c05d79d951ad3c80 # v1.8.0
+        uses: docker/setup-buildx-action@4d04d5d9486b7bd6fa91e7baf45bbb4f8b9deedd # v4.0.0
 
       - name: Build
-        uses: useblacksmith/build-push-action@fb9e3e6a9299c78462bfadd0d93352c316adc9b8 # v2.2.0
+        uses: docker/build-push-action@bcafcacb16a39f128d818304e6c9c0c18556b85f # v7.1.0
         with:
           platforms: linux/amd64
           push: false
@@ -104,7 +104,7 @@ jobs:
         uses: actions/checkout@de0fac2e4500dabe0009e67214ff5f5447ce83dd # v6.0.2
 
       - name: Set up Docker Buildx
-        uses: useblacksmith/setup-docker-builder@722e97d12b1d06a961800dd6c05d79d951ad3c80 # v1.8.0
+        uses: docker/setup-buildx-action@4d04d5d9486b7bd6fa91e7baf45bbb4f8b9deedd # v4.0.0
 
       - name: Login to Docker Hub
         uses: docker/login-action@4907a6ddec9925e35a0a9e82d7399ccc52663121 # v4.1.0
@@ -113,7 +113,7 @@ jobs:
           password: ${{ secrets.DOCKERHUB_TOKEN }}
 
       - name: Build and push
-        uses: useblacksmith/build-push-action@fb9e3e6a9299c78462bfadd0d93352c316adc9b8 # v2.2.0
+        uses: docker/build-push-action@bcafcacb16a39f128d818304e6c9c0c18556b85f # v7.1.0
         with:
           platforms: ${{ matrix.platform }}
           provenance: "true"
@@ -139,7 +139,7 @@ jobs:
         uses: actions/checkout@de0fac2e4500dabe0009e67214ff5f5447ce83dd # v6.0.2
 
       - name: Set up Docker Buildx
-        uses: useblacksmith/setup-docker-builder@722e97d12b1d06a961800dd6c05d79d951ad3c80 # v1.8.0
+        uses: docker/setup-buildx-action@4d04d5d9486b7bd6fa91e7baf45bbb4f8b9deedd # v4.0.0
 
       - name: Login to Huawei SWR
         uses: docker/login-action@4907a6ddec9925e35a0a9e82d7399ccc52663121 # v4.1.0
@@ -149,7 +149,7 @@ jobs:
           password: ${{ secrets.HUAWEI_SWR_TOKEN }}
 
       - name: Build and push
-        uses: useblacksmith/build-push-action@fb9e3e6a9299c78462bfadd0d93352c316adc9b8 # v2.2.0
+        uses: docker/build-push-action@bcafcacb16a39f128d818304e6c9c0c18556b85f # v7.1.0
         with:
           platforms: ${{ matrix.platform }}
           provenance: "false"
@@ -163,7 +163,7 @@ jobs:
 
     steps:
       - name: Set up Docker Buildx
-        uses: useblacksmith/setup-docker-builder@722e97d12b1d06a961800dd6c05d79d951ad3c80 # v1.8.0
+        uses: docker/setup-buildx-action@4d04d5d9486b7bd6fa91e7baf45bbb4f8b9deedd # v4.0.0
 
       - name: Login to Docker Hub
         uses: docker/login-action@4907a6ddec9925e35a0a9e82d7399ccc52663121 # v4.1.0
@@ -188,7 +188,7 @@ jobs:
 
     steps:
       - name: Set up Docker Buildx
-        uses: useblacksmith/setup-docker-builder@722e97d12b1d06a961800dd6c05d79d951ad3c80 # v1.8.0
+        uses: docker/setup-buildx-action@4d04d5d9486b7bd6fa91e7baf45bbb4f8b9deedd # v4.0.0
 
       - name: Login to Huawei SWR
         uses: docker/login-action@4907a6ddec9925e35a0a9e82d7399ccc52663121 # v4.1.0