1. CORS whitelist (was '*'): only buhapp.mygoodservice.ru, t.me, web.telegram.org
2. Rate limit on /auth/login (10/min/IP) and /auth/register (5/hour/IP)
3. TGHandler: removed unused JWTSecret, added WebhookSecret, real secret check
4. Login: constant-time bcrypt on user enumeration (dummy hash)
5. TgUsername saved in users (was lost)
6. User.IsVerified=true for Telegram users
7. Register: 409 instead of 500 on duplicate email
8. Bumped version to 0.4.0