Fix Gotify notifications with correct API format

- Use /message endpoint with form data instead of JSON
- Update notification provider to use correct Gotify URL
- Fix priority levels for different notification types
- Test notifications should now work properly

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude <noreply@anthropic.com>

flux-notification-provider.yaml

@@ -15,6 +15,4 @@ metadata:
   namespace: flux-system
 spec:
   type: generic
-  address: https://notify.caffeinetux.com
-  secretRef:
-    name: notify-token
+  address: https://notify.caffeinetux.com/message?token=APMvTuncQJmm6vd