Files saved into (server-side) read-only folders get deleted

### ⚠️ 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 have searched for 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

Files that are being moved to a folder that is read only on the server results in deletion of said files. This is highly unexpected.

It seems that this is a further regression, see #7797.

### Steps to reproduce

1. from another account, share a read-only folder
2. with your normal account, add a file to the now present read-only folder (i.e. `touch keepme.txt`)
3. wait for the client to run a sync cycle
4. verify that the file has now been deleted, contrary to expectation

### Expected behavior

At least, the files should not be touched at all.

Even better yet, the local folder should not be writable either, or a warning should be triggered that some files cannot be synced.

### Which files are affected by this bug

any

### Operating system

macOS

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

15.7.5

### Installation method

Official MacOS Installer

### Nextcloud Server version

33.0.5

### Nextcloud Desktop Client version

33.0.5

### Did this occur after an update or on a clean installation?

Minor version update (i.e. 33.0.0 → 33.0.1)

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

No

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

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

### Additional info

This is reproducible on Windows and MacOS, probably also Linux.