Three categories of fixes:
1. Goroutine leak causing 10-minute timeout:
- Add defer mon.notificationMgr.Stop() in monitor_memory_test.go
- Background goroutines from notification manager weren't being stopped
2. Database NULL column scanning errors:
- Change LastError from string to *string in queue.go
- Change PayloadBytes from int to *int in queue.go
- SQL NULL values require pointer types in Go
3. SSRF protection blocking test servers:
- Check allowlist for localhost before rejecting in notifications.go
- Set PULSE_DATA_DIR to temp directory in tests
- Add defer nm.Stop() calls to prevent goroutine leaks
Fixes for preflight test failures in workflow run 19280879903.
b41f8a2ac4