ci(claude-review): switch to pull_request_target for fork PR support

Fork PRs can't acquire an OIDC token or access secrets under
pull_request, so claude-code-action fails before review can run.
pull_request_target runs in the base repo's context, restoring both.

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

Author: tommysitu

.github/workflows/claude-code-review.yml

@@ -1,7 +1,7 @@
 name: Claude Code Review
 
 on:
-  pull_request:
+  pull_request_target:
     types: [opened, synchronize, ready_for_review, reopened]
     # Optional: Only run on specific file changes
     # paths: