feat: add TRIAL_DISABLED_FOR setting to disable trial by user type

New setting allows granular control over trial availability:
- none: trial available for all (default)
- email: trial disabled for email users
- telegram: trial disabled for telegram users
- all: trial disabled for everyone

Enforced in bot handlers, cabinet API, and miniapp routes.
Automatically appears in admin panel as dropdown via CHOICES.

app/webapi/routes/miniapp.py

@@ -3047,6 +3047,9 @@ def _is_trial_available_for_user(user: User) -> bool:
     if settings.TRIAL_DURATION_DAYS <= 0:
         return False
 
+    if settings.is_trial_disabled_for_user(getattr(user, 'auth_type', 'telegram')):
+        return False
+
     if getattr(user, 'has_had_paid_subscription', False):
         return False