ci(docker): use H200 runner for builds and add nightly GHCR workflow

.github/workflows/nightly-docker.yml

@@ -0,0 +1,50 @@
+name: Nightly Docker Build
+
+on:
+  schedule:
+    # 06:00 UTC daily — 2 hours before nightly benchmarks (08:00 UTC)
+    - cron: '0 6 * * *'
+  workflow_dispatch:
+
+concurrency:
+  group: nightly-docker
+  cancel-in-progress: true
+
+permissions:
+  contents: read
+  packages: write
+
+jobs:
+  build-and-push:
+    name: Build nightly Docker image
+    if: github.repository == 'lightseekorg/smg'
+    runs-on: ["8-gpu-h200"]
+    permissions:
+      contents: read
+      packages: write
+    steps:
+      - uses: actions/checkout@v6
+
+      - name: Set up QEMU
+        uses: docker/setup-qemu-action@v3
+
+      - name: Set up Docker Buildx
+        uses: docker/setup-buildx-action@v3
+
+      - name: Log in to GitHub Container Registry
+        uses: docker/login-action@v3
+        with:
+          registry: ghcr.io
+          username: ${{ github.actor }}
+          password: ${{ secrets.GITHUB_TOKEN }}
+
+      - name: Build and push
+        uses: docker/build-push-action@v6
+        with:
+          context: .
+          file: docker/Dockerfile
+          push: true
+          tags: ghcr.io/lightseekorg/smg:nightly
+          cache-from: type=gha
+          cache-to: type=gha,mode=max
+          platforms: linux/amd64,linux/arm64

.github/workflows/release-docker.yml

@@ -21,7 +21,7 @@ jobs:
   build-and-push:
     name: Build and push Docker image
     if: github.repository == 'lightseekorg/smg'
-    runs-on: ubuntu-latest
+    runs-on: ["8-gpu-h200"]
     permissions:
       contents: read
     steps: