feat: add support for Pushover notification provider

- Updated the list of supported notification provider types to include 'pushover'.
- Enhanced the notifications API tests to validate Pushover integration.
- Modified the notifications form to include fields specific to Pushover, such as API Token and User Key.
- Implemented CRUD operations for Pushover providers in the settings.
- Added end-to-end tests for Pushover provider functionality, including form rendering, payload validation, and security checks.
- Updated translations to include Pushover-specific labels and placeholders.

frontend/src/api/notifications.ts

@@ -1,6 +1,6 @@
 import client from './client';
 
-export const SUPPORTED_NOTIFICATION_PROVIDER_TYPES = ['discord', 'gotify', 'webhook', 'email', 'telegram', 'slack'] as const;
+export const SUPPORTED_NOTIFICATION_PROVIDER_TYPES = ['discord', 'gotify', 'webhook', 'email', 'telegram', 'slack', 'pushover'] 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' && type !== 'telegram' && type !== 'slack') {
+  if (type !== 'gotify' && type !== 'telegram' && type !== 'slack' && type !== 'pushover') {
     delete payload.token;
     return payload;
   }