fix: resolve sync 404 errors, user deletion FK constraint, and device limit not sent to RemnaWave

1. Remove pointless HWID reset during auto-sync deactivation — user
   doesn't exist in panel, API returns 404, UUID is cleaned up below.

2. Clean up RESTRICT FK references (AdminAuditLog, WithdrawalRequest,
   AdminRole, UserRole, AccessPolicy) before deleting user to prevent
   IntegrityError on admin_audit_log_user_id_fkey.

3. Fix device limit not being sent to RemnaWave when
   DEVICES_SELECTION_DISABLED_AMOUNT=0: treat 0 as "no forced override"
   instead of sending hwidDeviceLimit:0 (which Remnawave interprets as
   unlimited). Now falls through to subscription.device_limit from tariff.

4. Add info-level logging to POST /api/users (was debug) to match
   existing PATCH logging for device limit diagnostics.

app/config.py

@@ -1525,8 +1525,8 @@ class Settings(BaseSettings):
             logger.warning('Некорректное значение DEVICES_SELECTION_DISABLED_AMOUNT', raw_value=raw_value)
             return None
 
-        if value < 0:
-            return 0
+        if value <= 0:
+            return None
 
         return value