fix: Improve E2E test workflow for better backend debugging

Enhanced backend server startup in CI:
- Track server PID and process status
- Save logs to backend.log for debugging
- Better error detection with process monitoring
- Added cleanup step to kill server process
- Print backend logs on test failure

Improves reliability of E2E tests by providing better diagnostics when backend fails to start

.gitignore

@@ -87,4 +87,8 @@ docker-compose.override.yml
 .claude/hans/
 
 pnpm-lock.yaml
-yarn.lock
+yarn.lock
+
+# Fork-specific workflow files (should never be committed)
+DEVELOPMENT_WORKFLOW.md
+check-sync.sh