[Bug]: provide a better error message than Network Error: # on nextcloudcmd

### ⚠️ 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.
- [ ] I agree to follow Nextcloud's [Code of Conduct](https://nextcloud.com/contribute/code-of-conduct/)

### Bug description

The error message on the BulkPropagatorJob looks like this

> Could not complete propagation of ... by OCC::BulkPropagatorJob(0x557c662c70) with status OCC::SyncFileItem::NormalError and error: "Network error: 2"

The problem is it's just hard to figure out what the `2` or `5` or whatever means.

### Steps to reproduce

It's a log event.

### Expected behavior

Something like
> Network error: 2: got a HTTP 502 error code from the server"

### Which files are affected by this bug

https://github.com/nextcloud/desktop/blob/e32ff9d6a97de898d430b15241b06af0fcac6d6a/src/libsync/bulkpropagatorjob.cpp#L508

### Operating system

Linux

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

Raspbian

### Package

Distro package manager

### Nextcloud Server version

31.0.6

### Nextcloud Desktop Client version

Nextcloud version 3.7.3git

### 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 Enabled

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

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

### Nextcloud Server logs

```shell

```

### Additional info

https://github.com/nextcloud/desktop/issues/7001