fix: sync SUPPORT_SYSTEM_MODE between SystemSettings and SupportSettings

When changing SUPPORT_SYSTEM_MODE via system settings admin panel, the
SupportSettingsService JSON cache was not updated, causing the old value
to take priority. Now both services stay in sync bidirectionally.

app/services/support_settings_service.py

@@ -62,6 +62,7 @@ class SupportSettingsService:
             return False
         cls._load()
         cls._data['system_mode'] = mode_clean
+        settings.SUPPORT_SYSTEM_MODE = mode_clean
         return cls._save()
 
     # Main menu visibility

app/services/system_settings_service.py

@@ -1603,6 +1603,13 @@ class BotConfigurationService:
                     )
                 except Exception as error:
                     logger.error('Не удалось обновить сервис автосинхронизации RemnaWave', error=error)
+            elif key == 'SUPPORT_SYSTEM_MODE':
+                try:
+                    from app.services.support_settings_service import SupportSettingsService
+
+                    SupportSettingsService.set_system_mode(str(value))
+                except Exception as error:
+                    logger.error('Не удалось синхронизировать SupportSettingsService', error=error)
             elif key in {
                 'REMNAWAVE_API_URL',
                 'REMNAWAVE_API_KEY',