ci: add upstream sync workflow

.github/workflows/sync.yml

@@ -0,0 +1,42 @@
+name: Sync Upstream
+
+env:
+  UPSTREAM_URL: "https://github.com/binaricat/Netcatty.git"
+  UPSTREAM_BRANCH: "main"
+  TARGET_BRANCH: "main"
+
+on:
+  schedule:
+    - cron: '0 0 * * *'  # Run daily at midnight
+  workflow_dispatch:      # Allow manual trigger
+
+jobs:
+  sync:
+    runs-on: ubuntu-latest
+    permissions:
+      contents: write
+    steps:
+      - name: Checkout
+        uses: actions/checkout@v4
+        with:
+          ref: ${{ env.TARGET_BRANCH }}
+          fetch-depth: 0
+          token: ${{ secrets.GITHUB_TOKEN }}
+
+      - name: Configure Git
+        run: |
+          git config --global user.name "github-actions[bot]"
+          git config --global user.email "github-actions[bot]@users.noreply.github.com"
+
+      - name: Merge Upstream
+        run: |
+          echo "Adding upstream remote..."
+          git remote add upstream ${{ env.UPSTREAM_URL }}
+          git fetch upstream ${{ env.UPSTREAM_BRANCH }}
+          
+          echo "Merging upstream/${{ env.UPSTREAM_BRANCH }} into ${{ env.TARGET_BRANCH }}..."
+          # This will fail if there are conflicts, which is the desired behavior (notify user via failure)
+          git merge upstream/${{ env.UPSTREAM_BRANCH }} --no-edit
+          
+          echo "Pushing changes..."
+          git push origin ${{ env.TARGET_BRANCH }}