Add webhook and Connect notification support

[rroy676]

Goal

Add an arr-style Settings → Connect system so Stationarr can notify external services when important events happen.

Problem

Stationarr currently does not have a general notification/connect system. Users need to manually check the UI or Docker logs to know when playlist refreshes fail, EPG fetches fail, scraper runs return 0 programme entries, or updates are available.

Arr ecosystem users expect a Connect/Notifications area where events can be sent to webhooks or other services.

Expected behaviour

Add Settings → Connect with notification targets such as:

- Webhook
- Discord, later
- Slack, later
- Email, later
- Home Assistant webhook, later

First version can focus on generic webhooks.

Suggested events

- Playlist imported
- Playlist refresh succeeded
- Playlist refresh failed
- EPG fetch succeeded
- EPG fetch failed
- EPG scraper run succeeded
- EPG scraper generated 0 programme entries
- EPG scraper/source warning
- Update available
- Health warning created or cleared

Suggested webhook payload

{
  "app": "Stationarr",
  "event": "playlist_refresh_failed",
  "level": "error",
  "title": "Playlist refresh failed",
  "message": "HTTP 451 while refreshing playlist source",
  "playlist_id": 1,
  "playlist_name": "Example Playlist",
  "timestamp": "2026-05-20T10:40:00Z"
}

Requirements

• Allow users to configure one or more webhook URLs.
• Allow users to choose which events trigger each webhook.
• Provide a test notification button.
• Avoid sending secrets, API keys, passwords, or full sensitive playlist URLs.
• Handle webhook failures gracefully.
• Log notification send failures without crashing the app.

Validation

• Configure a webhook URL.
• Send a test notification.
• Trigger a playlist refresh failure and confirm a webhook is sent.
• Trigger a scraper 0-programme warning and confirm a webhook is sent.
• Confirm sensitive values are not included in payloads.

Related

Part of making Stationarr feel more native to the arr/self-hosted ecosystem. Related to Home Assistant support (#43), System Health (#45), and Activity/History (#47).