[Bug]: Enabling VFS on Linux with a read-only share fails with permission denied errors

### ⚠️ 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

Enabling virtual file support on a share with read-only access does not work; and reports permission denied.

(Presumably because the 'rename' to `filename.nextcloud` is blocked.)

### Steps to reproduce

1. Have a share with read-only access.
2. Enable virtual file support.
3. Nextcloud starts reporting permission denied on the files in the share.

### Expected behavior

1. Have a share with read-only access.
2. Enable virtual file support.
3. Nextcloud starts syncing files successfully.

### Which files are affected by this bug

77 kwakkel.JPG

### Operating system

Linux

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

Fedora 41

### Package

Community FlatPak

### Nextcloud Server version

30.0.9

### Nextcloud Desktop Client version

3.15.3

### 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?

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

### Nextcloud Server logs

```shell
No server side messaging
```

### Additional info

[Nextcloud.client.zip](https://github.com/user-attachments/files/19834503/Nextcloud.client.zip)

Reproduce the failure with the Linux Community FlatPak client, a read-only share, virtual file support, and 77 kwakkel.JPG; the issue names no source file or test to start from. Compare the permission-denied behavior with the expected successful sync, using the attached Nextcloud.client.zip for diagnostic details.

Written by the indexing model from the issue text.