fix: restrict milestone assignment workflow to specific event types for issues and pull requests

Author: JhaSourav07

.github/workflows/milestone-manager.yml

@@ -13,8 +13,8 @@ permissions:
 jobs:
   assign-to-milestone:
     if: >
-      github.event.label.name == 'GSSoC 2026' ||
-      github.event.label.name == 'gssoc:approved'
+      (github.event_name == 'issues' && github.event.label.name == 'GSSoC 2026') ||
+      (github.event_name == 'pull_request_target' && github.event.label.name == 'gssoc:approved')
     runs-on: ubuntu-latest
     steps:
       - name: Assign to GSSoC 2026 Milestone