ci: add GitHub Actions workflows for upstream sync and release automation

.github/workflows/upstream-sync.yml

@@ -0,0 +1,48 @@
+name: Upstream Sync Build
+
+on:
+  push:
+    branches:
+      - dev
+
+env:
+  DOCKER_IMAGE: convertx/convertx-cn
+
+jobs:
+  build-and-push:
+    runs-on: ubuntu-latest
+    
+    steps:
+      - name: Checkout repository
+        uses: actions/checkout@v4
+
+      - name: Get current date
+        id: date
+        run: echo "date=$(date +'%Y%m%d')" >> $GITHUB_OUTPUT
+
+      - name: Set up Docker Buildx
+        uses: docker/setup-buildx-action@v3
+
+      - name: Login to Docker Hub
+        uses: docker/login-action@v3
+        with:
+          username: ${{ secrets.DOCKERHUB_USERNAME }}
+          password: ${{ secrets.DOCKERHUB_TOKEN }}
+
+      - name: Build and push Docker image
+        uses: docker/build-push-action@v6
+        with:
+          context: .
+          push: true
+          tags: ${{ env.DOCKER_IMAGE }}:upstream-${{ steps.date.outputs.date }}
+          platforms: linux/amd64,linux/arm64
+          cache-from: type=gha
+          cache-to: type=gha,mode=max
+
+      - name: Summary
+        run: |
+          echo "## 🐳 Docker Image Published" >> $GITHUB_STEP_SUMMARY
+          echo "" >> $GITHUB_STEP_SUMMARY
+          echo "**Image:** \`${{ env.DOCKER_IMAGE }}:upstream-${{ steps.date.outputs.date }}\`" >> $GITHUB_STEP_SUMMARY
+          echo "" >> $GITHUB_STEP_SUMMARY
+          echo "This is an upstream sync build. Use version tags for stable releases." >> $GITHUB_STEP_SUMMARY