[Bug]: notifications should be synced across open browser tabs

[alexanderdd]

⚠️ This issue respects the following points: ⚠️

• This is a bug, not a question or a configuration/webserver/proxy issue.
• This issue is not already reported on Github OR Nextcloud Community Forum (I've searched it).
• Nextcloud Server is up to date. See Maintenance and Release Schedule for supported versions.
• I agree to follow Nextcloud's Code of Conduct.

Steps to reproduce

1. have multiple tabs with NC open
2. receive notifications
3. dismiss notifications in one tab
4. go to different tab
5. the dismissed notifications are still there

Expected behavior

• notifications should be synced across open browser tabs
• dismissed notifications should be dismissed in all browser tabs

Nextcloud Server version

30

Additional info

it is very common that people have NC open in multiple tabs/windows

it is confusing that a user action in one tab is not respected in another tab

maybe related? #13980