feat: Implement notification system with Apprise integration and credential checks

.env.demo

@@ -124,6 +124,26 @@ SFTP_PASSWORD=your_secure_sftp_password
 # SFTP_PRIVATE_KEY_PASSPHRASE=optional_passphrase
 SFTP_FOLDER=/Documents/Uploads
 
+# **Notification Settings**
+# Configure notification services using Apprise URL format
+# See https://github.com/caronc/apprise#supported-notifications
+# Examples:
+# - Discord: discord://webhook_id/webhook_token
+# - Telegram: tgram://bot_token/chat_id
+# - Email: mailto://user:pass@example.com
+# - Pushover: pover://user_key/app_token
+# - Slack: slack://tokenA/tokenB/tokenC
+# - Matrix: matrix://username:password@domain/#room
+
+# You can specify multiple notification URLs by separating them with commas
+NOTIFICATION_URLS=discord://webhook_id/webhook_token,mailto://user:pass@gmail.com,tgram://bot_token/chat_id
+
+# Control when notifications are sent
+NOTIFY_ON_TASK_FAILURE=True
+NOTIFY_ON_CREDENTIAL_FAILURE=True
+NOTIFY_ON_STARTUP=True
+NOTIFY_ON_SHUTDOWN=False
+
 # Uptime Kuma
 UPTIME_KUMA_URL=https://status.example.com/api/push/abcdef123456?status=up
 UPTIME_KUMA_PING_INTERVAL=5