Initial minimal Flutter SDK image for web/WASM CI builds

- Dockerfile based on debian:bookworm-slim with web-only Flutter SDK
- Release pipeline with Docker Scout CVE scan, SBOM, and provenance
- Scout PR pipeline with check-image gate
- Daily update-check pipeline that auto-creates releases for new
  Flutter stable versions via Gitea API

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

.gitea/workflows/publish.yaml

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+name: Build and Push Flutter SDK Image
+
+on:
+  release:
+    types: [published, prereleased]
+
+permissions:
+  contents: read
+
+env:
+  IMAGE_NAME: gpb-flutter-sdk-web
+
+jobs:
+  build-and-push:
+    runs-on: ubuntu-latest
+    steps:
+      - name: Checkout code
+        uses: actions/checkout@v3
+
+      - name: Determine Tag Type
+        id: tag_type
+        run: |
+          if [[ "${{ github.event.release.prerelease }}" == "true" ]]; then
+            echo "tag=dev" >> $GITHUB_OUTPUT
+          else
+            echo "tag=latest" >> $GITHUB_OUTPUT
+          fi
+
+      - name: Set up Docker Buildx
+        uses: docker/setup-buildx-action@v3
+
+      - name: Login to Docker Registry
+        uses: docker/login-action@v3
+        with:
+          username: ${{ secrets.DOCKERHUB_SVRNTY_USERNAME }}
+          password: ${{ secrets.DOCKERHUB_SVRNTY_ACCESS_TOKEN }}
+
+      - name: Build image for Scout analysis
+        uses: docker/build-push-action@v5
+        with:
+          context: .
+          platforms: linux/amd64
+          push: false
+          load: true
+          build-args: |
+            FLUTTER_VERSION=${{ github.event.release.tag_name }}
+          tags: ${{ vars.REGISTRY }}/${{ env.IMAGE_NAME }}:${{ github.event.release.tag_name }}
+
+      - name: Install Docker Scout
+        run: |
+          curl -fsSL https://raw.githubusercontent.com/docker/scout-cli/main/install.sh -o install-scout.sh
+          sh install-scout.sh
+
+      - name: Docker Scout CVE Scan
+        run: |
+          docker scout cves ${{ vars.REGISTRY }}/${{ env.IMAGE_NAME }}:${{ github.event.release.tag_name }} --only-severity critical,high
+
+      - name: Build and push with attestations
+        uses: docker/build-push-action@v5
+        with:
+          context: .
+          platforms: linux/amd64
+          push: true
+          sbom: true
+          provenance: mode=max
+          build-args: |
+            FLUTTER_VERSION=${{ github.event.release.tag_name }}
+          tags: |
+            ${{ vars.REGISTRY }}/${{ env.IMAGE_NAME }}:${{ github.event.release.tag_name }}
+            ${{ vars.REGISTRY }}/${{ env.IMAGE_NAME }}:${{ steps.tag_type.outputs.tag }}
+          labels: |
+            org.opencontainers.image.title=${{ env.IMAGE_NAME }}
+            org.opencontainers.image.description=Minimal Flutter SDK for Web/WASM CI builds
+            org.opencontainers.image.version=${{ github.event.release.tag_name }}
+            org.opencontainers.image.revision=${{ github.sha }}

.gitea/workflows/scout.yaml

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+name: Docker Scout Analysis
+
+on:
+  pull_request:
+    branches: ["**"]
+
+permissions:
+  contents: read
+  pull-requests: write
+
+env:
+  IMAGE_NAME: gpb-flutter-sdk-web
+
+jobs:
+  check-image:
+    runs-on: ubuntu-latest
+    outputs:
+      image_exists: ${{ steps.check.outputs.exists }}
+    steps:
+      - name: Log in to DockerHub
+        uses: docker/login-action@v3
+        with:
+          username: ${{ secrets.DOCKERHUB_SVRNTY_USERNAME }}
+          password: ${{ secrets.DOCKERHUB_SVRNTY_ACCESS_TOKEN }}
+
+      - name: Check if latest image exists
+        id: check
+        run: |
+          if docker manifest inspect ${{ vars.REGISTRY }}/${{ env.IMAGE_NAME }}:latest > /dev/null 2>&1; then
+            echo "exists=true" >> $GITHUB_OUTPUT
+            echo "Latest image found, Scout compare will run"
+          else
+            echo "exists=false" >> $GITHUB_OUTPUT
+            echo "No latest image found, skipping Scout compare (nothing to compare against)"
+          fi
+
+  scout-amd64:
+    runs-on: ubuntu-latest
+    needs: check-image
+    if: needs.check-image.outputs.image_exists == 'true'
+    steps:
+      - name: Checkout code
+        uses: actions/checkout@v3
+
+      - name: Set up Docker Buildx
+        uses: docker/setup-buildx-action@v3
+
+      - name: Log in to DockerHub
+        uses: docker/login-action@v3
+        with:
+          username: ${{ secrets.DOCKERHUB_SVRNTY_USERNAME }}
+          password: ${{ secrets.DOCKERHUB_SVRNTY_ACCESS_TOKEN }}
+
+      - name: Build amd64 image
+        uses: docker/build-push-action@v5
+        with:
+          context: .
+          platforms: linux/amd64
+          push: false
+          load: true
+          tags: ${{ vars.REGISTRY }}/${{ env.IMAGE_NAME }}:pr-${{ github.event.pull_request.number }}-amd64
+
+      - name: Install Docker Scout
+        run: |
+          curl -fsSL https://raw.githubusercontent.com/docker/scout-cli/main/install.sh -o install-scout.sh
+          sh install-scout.sh
+
+      - name: Docker Scout Compare (amd64)
+        run: |
+          docker scout compare ${{ vars.REGISTRY }}/${{ env.IMAGE_NAME }}:pr-${{ github.event.pull_request.number }}-amd64 --to ${{ vars.REGISTRY }}/${{ env.IMAGE_NAME }}:latest --ignore-unchanged --only-severity critical,high

.gitea/workflows/update-check.yaml

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+name: Check for Flutter SDK Updates
+
+on:
+  schedule:
+    - cron: '0 8 * * *'
+  workflow_dispatch:
+
+jobs:
+  check-update:
+    runs-on: ubuntu-latest
+    steps:
+      - name: Get latest Flutter stable version
+        id: flutter
+        run: |
+          LATEST=$(curl -fsSL https://storage.googleapis.com/flutter_infra_release/releases/releases_linux.json \
+            | jq -r '.current_release.stable as $hash | .releases[] | select(.hash == $hash) | .version')
+          echo "version=${LATEST}" >> $GITHUB_OUTPUT
+          echo "Latest Flutter stable: ${LATEST}"
+
+      - name: Check if release already exists
+        id: existing
+        run: |
+          VERSION="${{ steps.flutter.outputs.version }}"
+          STATUS=$(curl -s -o /dev/null -w "%{http_code}" \
+            "${{ github.server_url }}/api/v1/repos/${{ github.repository }}/releases/tags/${VERSION}")
+          if [ "$STATUS" = "200" ]; then
+            echo "exists=true" >> $GITHUB_OUTPUT
+            echo "Release ${VERSION} already exists, skipping"
+          else
+            echo "exists=false" >> $GITHUB_OUTPUT
+            echo "Release ${VERSION} not found, will create"
+          fi
+
+      - name: Create release for new version
+        if: steps.existing.outputs.exists == 'false' && steps.flutter.outputs.version != ''
+        run: |
+          VERSION="${{ steps.flutter.outputs.version }}"
+          echo "Creating release for Flutter ${VERSION}"
+          curl -fsSL -X POST \
+            -H "Authorization: token ${{ secrets.GITEA_TOKEN }}" \
+            -H "Content-Type: application/json" \
+            "${{ github.server_url }}/api/v1/repos/${{ github.repository }}/releases" \
+            -d "{
+              \"tag_name\": \"${VERSION}\",
+              \"name\": \"Flutter SDK ${VERSION}\",
+              \"body\": \"Automated release for Flutter stable ${VERSION}\",
+              \"draft\": false,
+              \"prerelease\": false
+            }"

.gitignore

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+.DS_Store

Dockerfile

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+FROM debian:bookworm-slim
+
+ARG FLUTTER_VERSION=3.38.9
+
+LABEL org.opencontainers.image.title="gpb-flutter-sdk-web"
+LABEL org.opencontainers.image.description="Minimal Flutter SDK for Web/WASM CI builds"
+LABEL org.opencontainers.image.version="${FLUTTER_VERSION}"
+
+# Install minimal dependencies for Flutter web builds
+RUN apt-get update && apt-get install -y --no-install-recommends \
+    curl \
+    git \
+    unzip \
+    xz-utils \
+    ca-certificates \
+    && rm -rf /var/lib/apt/lists/*
+
+ENV FLUTTER_HOME=/opt/flutter
+ENV PATH="${FLUTTER_HOME}/bin:${FLUTTER_HOME}/bin/cache/dart-sdk/bin:${PATH}"
+
+# Download Flutter SDK from official archive
+RUN curl -fsSL "https://storage.googleapis.com/flutter_infra_release/releases/stable/linux/flutter_linux_${FLUTTER_VERSION}-stable.tar.xz" \
+      -o /tmp/flutter.tar.xz && \
+    tar xf /tmp/flutter.tar.xz -C /opt && \
+    rm /tmp/flutter.tar.xz
+
+# Mark git directory as safe (tarball is owned by different uid)
+RUN git config --global --add safe.directory "${FLUTTER_HOME}"
+
+# Configure for web-only (disable everything else)
+RUN flutter config --enable-web \
+    --no-enable-android \
+    --no-enable-ios \
+    --no-enable-linux-desktop \
+    --no-enable-macos-desktop \
+    --no-enable-windows-desktop
+
+# Precache only web artifacts
+RUN flutter precache --web \
+    --no-android \
+    --no-ios \
+    --no-linux \
+    --no-macos \
+    --no-windows \
+    --no-fuchsia \
+    --no-universal
+
+# Verify installation
+RUN flutter doctor -v
+
+WORKDIR /app