ci(build.yaml): add a guard step to skip builds for PRs targeting master or dev branches

.gitea/workflows/build.yaml

@@ -7,6 +7,17 @@ jobs:
     runs-on: ubuntu-latest
 
     steps:
+      - name: Check if PR targets master/dev
+        id: guard
+        run: |
+          if [ "${{ github.base_ref }}" = "master" ] || [ "${{ github.base_ref }}" = "dev" ]; then
+            echo "skip_build=true" >> $GITHUB_ENV
+            echo "This PR targets '${{ github.base_ref }}', skipping build (handled by deploy workflow)."
+          else
+            echo "skip_build=false" >> $GITHUB_ENV
+            echo "This PR targets '${{ github.base_ref }}', proceeding with build."
+          fi
+
       - name: Checkout Repository
         uses: actions/checkout@v2