[Bug]: Shared folder notifications never disappear in desktop client

### ⚠️ Before submitting, please verify the following: ⚠️

- [x] This is a **bug**, not a question or a configuration issue.
- [x] This issue is **not** already reported on Github (I've searched it).
- [x] Nextcloud Server and Desktop Client are **up to date**. See [Server Maintenance and Release Schedule](https://github.com/nextcloud/server/wiki/Maintenance-and-Release-Schedule) and [Desktop Releases](https://nextcloud.com/install/#install-clients) for supported versions.
- [x] I agree to follow Nextcloud's [Code of Conduct](https://nextcloud.com/contribute/code-of-conduct/)

### Bug description

When another user shares a folder with you, the Nextcloud desktop client displays a notification like
`@User shared Shared/yyyy-mm-dd FolderName` with you.

The problem is that these notifications never disappear, even after days or weeks, and even after the folder is synchronized and accessed.
Over time, the notifications list fills with dozens of entries, making it hard to check the actual sync status without scrolling a lot.

Example: In my case, some notifications are still visible more than 90 days after the share event. There is also no button or menu option to clear or dismiss them.

### Steps to reproduce

1. Have User A share a folder with User B in Nextcloud.
2. On User B’s machine, open the Nextcloud desktop client.
3. See the notification that the folder has been shared.
4. Wait several days/weeks. The notification will remain indefinitely.
5. Try to find an option to dismiss or clear it, I couldn't find any.

### Expected behavior

Notifications should either:

- auto-clear after the folder is synchronized, or
- allow the user to dismiss them manually, so the notifications list remains useful for current sync information.

### Which files are affected by this bug

Not specific to a file, it affects all folders shared between users.

### Operating system

Windows

### Which version of the operating system you are running.

Windows 10 22H2

### Package

Official Windows MSI

### Nextcloud Server version

31.0.8

### Nextcloud Desktop Client version

3.17.0

### Is this bug present after an update or on a fresh install?

Fresh desktop client install

### Are you using the Nextcloud Server Encryption module?

Encryption is Disabled

### Are you using an external user-backend?

- [ ] Default internal user-backend
- [ ] LDAP/ Active Directory
- [ ] SSO - SAML
- [ ] Other

### Nextcloud Server logs

```shell
No relevant errors found in `nextcloud.log` related to these notifications.
```

### Additional info

The issue makes the notification area unusable for its main purpose (tracking sync status).

Screenshot attached for reference.