ci: run CI/CD for PRs targeting release/v* branches

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

Author: olivermeyer

.github/workflows/ci-cd.yml

@@ -8,7 +8,9 @@ on:
     tags:
       - "v*.*.*"
   pull_request:
-    branches: [main]
+    branches:
+      - "main"
+      - "release/v*"
     types: [opened, synchronize, reopened]
   release:
     types: [created]