[Bug]: Confusing e2ee user experience

### ⚠️ 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

I had a really hard time to find out how to actually initialize an encrypted folder using the desktop client. [The documentation](https://github.com/nextcloud/end_to_end_encryption?tab=readme-ov-file#establishing-a-folder-to-encrypt) is rather scarce here, I opened [a PR to improve it a bit](https://github.com/nextcloud/end_to_end_encryption/pull/998).

I had expected the client to offer enabling encryption when setting up a new folder synchronization. I created a new folder that way and after not being offered that option searched any possible menu/settings in the client to make the new folder encrypted afterwards. It took me 15 minutes to have the idea of creating another subfolder in this new folder synchronization and another 5 minutes to right-click on this subfolder in the desktop client in order to finally spot the "Encrypt" option there.

### Steps to reproduce

Try to enable e2e encryption for a root folder of a configured folder synchronization.

### Expected behavior

I guess my suggestions for improvement in the desktop client would be the following:

1. Allow to e2e-encrypt the root folder of a new folder synchronization and provide the option to enable encryption in the dialogs while setting up the new folder synchronization.
2. Add the "Encrypt" option to the three-dots menu of each folder synchronization instead of just the context menu of further subfolders.

### Which files are affected by this bug

...

### Operating system

Linux

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

Debian Bookworm

### Package

Community FlatPak

### Nextcloud Server version

30

### 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?

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

### Nextcloud Server logs

```shell

```

### Additional info

_No response_