[Bug]: Contents of sync folder removed during temporary problem with app auth

### ⚠️ 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

Laptop synced to Nextcloud server with relatively large filesystem (say >200GB), probably over 100GB of hydrated files.

Whilst conducting maintenance, I un-ticked the "Allow file system access" mark on the Nextcloud server. (I had mis-identified which auth token was no-longer used, and de-selected this option as it seemed like it would just (perhaps) prevent login or present an error. (Other options only being "Revoke" or "Wipe device").

Time passes, and I later discover that the desktop client response to this (temporary) situation has been to wipe out my entire sync'd folder on the laptop - effectively scrapping all the metadata it had sync'd and tens / hundreds of gigabytes in hydrated files.

Fortunately my instance was synced with the server, so I haven't actually lost any data - but ultimately, the behaviour was unexpected. (I imagine it would have potentially caused data-loss if laptop folder had un-sync'd / newer versions of files than on the server).

..

### Steps to reproduce

1. Sync files to client
2. De-select "Allow filesystem access" for auth-token the app authenticates vi
3. Client wipes files.

...

### Expected behavior

I had anticipated the sync client would pause syncing, or fail to log into the server to retrieve files.

Client wiping behavior is explicitly unexpected since there is a separate option you can select for "Wipe device" when managing auth tokens.

...

### Which files are affected by this bug

ALL files

### Operating system

Windows

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

Windows 10

### Package

Official Windows MSI

### Nextcloud Server version

31.0.7

### Nextcloud Desktop Client version

Daily, windows-20250728.msi Reverted to 3.17.0 rc1 now.

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

Updated from a minor version (ex. 3.4.2 to 3.4.4)

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

Encryption is Disabled

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

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

### Nextcloud Server logs

```shell
No relevant logs on server
```

### Additional info

I have not uploaded logs, as the subsequent resync of metadata seems to have caused them to roll over (no logs remain from the actual deletion).