feat: add Telegram notification provider support

- Updated API to support Telegram as a notification provider type.
- Enhanced tests to cover Telegram provider creation, updates, and token handling.
- Modified frontend forms to include Telegram-specific fields and validation.
- Added localization strings for Telegram provider.
- Implemented security measures to ensure bot tokens are not exposed in API responses.

frontend/src/api/notifications.ts

@@ -1,6 +1,6 @@
 import client from './client';
 
-export const SUPPORTED_NOTIFICATION_PROVIDER_TYPES = ['discord', 'gotify', 'webhook', 'email'] as const;
+export const SUPPORTED_NOTIFICATION_PROVIDER_TYPES = ['discord', 'gotify', 'webhook', 'email', 'telegram'] as const;
 export type SupportedNotificationProviderType = (typeof SUPPORTED_NOTIFICATION_PROVIDER_TYPES)[number];
 const DEFAULT_PROVIDER_TYPE: SupportedNotificationProviderType = 'discord';
 
@@ -59,7 +59,7 @@ const sanitizeProviderForWriteAction = (data: Partial<NotificationProvider>): Pa
 
   delete payload.gotify_token;
 
-  if (type !== 'gotify') {
+  if (type !== 'gotify' && type !== 'telegram') {
     delete payload.token;
     return payload;
   }