Changed from configurable count input to three separate buttons for
success, warning, and error test emails. Each button generates exactly
3 emails with consistent data for reproducible testing.
Changes:
- Updated routes_settings.py to use fixed email sets instead of random data
- Changed route from /settings/test-emails/generate to /settings/test-emails/generate/<status_type>
- Created three predefined email sets (success, warning, error) with fixed content
- Updated settings.html UI to show three separate buttons instead of count input
- Each set contains 3 emails simulating Veeam, Synology, and NAKIVO backups
- Updated changelog with detailed description
Co-Authored-By: Claude Sonnet 4.5 <noreply@anthropic.com>