[Bug]: 3.17.0 Proxy Handling Broken

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- [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).
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### Bug description

When using the 3.17.0 desktop client on Ubuntu 24.04 I am unable to add or use accounts in conjunction with SOCKS proxies.

This has been tested with upgrading from 3.16.0 to 3.17.0 and with a fresh desktop installation of 3.17.0 on a Ubuntu 24.04 VM.

Tested versions that do not display the issue are 3.16.0, 3.16.4, and 3.16.6

### Steps to reproduce

1a. Fresh install of Ubuntu and newly downloaded AppImage for 3.17.0
2a. Attempt to add account with system proxy (it will fail to connect to the Nextcloud server through the socks proxy with no way to modify the behavior in the GUI until after account is added)

1b. Fresh install of Ubuntu and newly downloaded AppImage for 3.17.0
2b. Attempt to add account with direct network access to Nextcloud server, it will succeed.
3b. Modify user SOCKS proxy settings
4b. Attempt to use SOCKS proxy without direct network access to Nextcloud server, it will fail but settings will persist.
...

### Expected behavior

In previous versions it was possible to modify the network settings before adding an account, which is needed to reach the Nextcloud server and sync files in my instance. This can be seen in the following image.

In 3.17.0 that option has been removed and is restricted until an account has been added successfully:

The proxy setting in 3.17.0 is available in individual user settings once one has been added to the desktop client in but does not handle forwarding properly.

Even when an account is added with direct connection to the Nextcloud server with the desktop client 3.17.0 and SOCKS settings are set in the desktop client GUI after an account has been added communication fails on attempting to rely on that SOCKS proxy.

### Which files are affected by this bug

desktop client (likely ~/.config/Nextcloud/nextcloud.cfg)

### Operating system

Linux

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

Ubunto 24.04

### Package

Official Linux AppImage

### Nextcloud Server version

31.0.7

### 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 Enabled

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

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

### Nextcloud Server logs

```shell

```

### Additional info

When direct access is granted to the Nextcloud server in order to add an account it is added successfully and the SOCKS settings can be changed to the desired configuration. However upon disconnecting and attempting to reconnect over the SOCKS proxy, it will continue to fail despite working in earlier versions of Nextcloud.
It also appears that the default behavior is to use no proxy when an account has been added, I am not sure if this would affect initial or upgrade behavior (This appears to contrast 3.16.6 observed behavior which defaults to system proxy).

Manually adding (or copying old proxy config from 3.16) to the local Nextcloud configuration files also does not change this behavior and it is not possible to add accounts to the desktop client.