feat: add stable release branch support

- Add release/stable branch to CI workflow
- Create docker-compose.stable.yml with :stable tag
- Create install-stable.sh for one-click deployment
- Add stable tag creation in manifest step

.github/workflows/docker-build.yml

@@ -5,6 +5,7 @@ on:
     branches:
       - main
       - dev
+      - release/stable
     tags:
       - 'v*'
   pull_request:
@@ -171,6 +172,14 @@ jobs:
             echo "✅ Created latest tag (main branch only)"
           fi
 
+          # release/stable branch gets the 'stable' tag
+          if [[ "${{ github.ref }}" == "refs/heads/release/stable" ]]; then
+            docker buildx imagetools create -t "${GHCR_IMAGE}:stable" \
+              "${GHCR_IMAGE}:${REF_NAME}-amd64" \
+              "${GHCR_IMAGE}:${REF_NAME}-arm64"
+            echo "✅ Created stable tag (release/stable branch)"
+          fi
+
           if [[ -n "${{ secrets.DOCKERHUB_USERNAME }}" ]]; then
             DOCKERHUB_IMAGE="${{ secrets.DOCKERHUB_USERNAME }}/nofx-${{ matrix.image_suffix }}"
             docker buildx imagetools create -t "${DOCKERHUB_IMAGE}:${REF_NAME}" \