feat: Allow assigned admins to access admin panel via command and buttons

- Modified check_admin_access() to check both super admins (.env) and assigned admins (DB)
- Updated /admin command handler to support both admin types
- Replaced all is_admin() checks with async check_admin_access() in admin panel
- Assigned admins can now use /admin command and navigate via buttons
- Super admin check (is_super_admin) remains unchanged for admin management
- Added proper async/await for database queries in all admin checks

.gitignore

@@ -60,3 +60,4 @@ venv.bak/
 # Системные файлы
 .DS_Store
 Thumbs.db.bot.pid
+*.bak