fix(ci): use plain docker build/push instead of buildx

buildx pulls moby/buildkit from Docker Hub which hits rate limits.
Plain docker build+push avoids this entirely since base images are
already cached on the runner.

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

Author: maderwin

.github/workflows/ci.yml

@@ -43,21 +43,13 @@ jobs:
     steps:
       - uses: actions/checkout@v4
 
-      - name: Set up Docker Buildx
-        uses: docker/setup-buildx-action@v3
-
       - name: Login to YC Container Registry
-        uses: docker/login-action@v3
-        with:
-          registry: cr.yandex
-          username: json_key
-          password: ${{ secrets.YC_SA_KEY_JSON }}
+        run: echo '${{ secrets.YC_SA_KEY_JSON }}' | docker login cr.yandex -u json_key --password-stdin
 
-      - name: Build and push
-        uses: docker/build-push-action@v6
-        with:
-          context: .
-          push: true
-          tags: |
-            cr.yandex/crpml6ifd12s8cbmbg3m/atlas:latest
-            cr.yandex/crpml6ifd12s8cbmbg3m/atlas:${{ github.sha }}
+      - name: Build
+        run: docker build -t cr.yandex/crpml6ifd12s8cbmbg3m/atlas:latest -t cr.yandex/crpml6ifd12s8cbmbg3m/atlas:${{ github.sha }} .
+
+      - name: Push
+        run: |
+          docker push cr.yandex/crpml6ifd12s8cbmbg3m/atlas:latest
+          docker push cr.yandex/crpml6ifd12s8cbmbg3m/atlas:${{ github.sha }}