fix: disable provenance to fix multi-arch manifest creation

Buildx with provenance creates manifest lists even for single-platform
builds. This breaks `docker manifest create` which expects plain images.

Adding provenance: false ensures plain images are pushed, allowing
the manifest creation step to work correctly.

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

.github/workflows/main.yml

@@ -36,6 +36,7 @@ jobs:
         uses: docker/build-push-action@v5
         with:
           context: .
+          provenance: false
           platforms: linux/arm64
           cache-from: type=registry,ref=${{ env.REGISTRY }}/${{ env.IMAGE_NAME }}:buildcache-arm64
           cache-to: type=registry,ref=${{ env.REGISTRY }}/${{ env.IMAGE_NAME }}:buildcache-arm64,mode=max
@@ -66,6 +67,7 @@ jobs:
         uses: docker/build-push-action@v5
         with:
           context: .
+          provenance: false
           platforms: linux/amd64
           cache-from: type=registry,ref=${{ env.REGISTRY }}/${{ env.IMAGE_NAME }}:buildcache-amd64
           cache-to: type=registry,ref=${{ env.REGISTRY }}/${{ env.IMAGE_NAME }}:buildcache-amd64,mode=max