ci: restrict release workflow to main (#2187)

.github/workflows/release.yml

@@ -17,6 +17,12 @@ jobs:
       version: ${{ steps.set-version.outputs.version }}
       image-version: ${{ steps.set-image-version.outputs.image-version }}
     steps:
+      - name: Validate release branch
+        if: ${{ github.ref != 'refs/heads/main' }}
+        run: |
+          echo "::error::Releases must be triggered from the main branch. Selected ref: ${{ github.ref }}"
+          exit 1
+
       - name: Checkout code
         uses: actions/checkout@de0fac2e4500dabe0009e67214ff5f5447ce83dd # v6.0.0
         with: