Main window may become unusable at low screen resolution

### Please answer the following questions for yourself before submitting an issue.

- [x] I checked the [knowledge base](https://adguard-vpn.com/kb/) and found no answer
- [x] I checked to make sure that this issue has not already been filed

### AdGuard VPN version

`2.9.2004.0`, `2.9.2042.0`

### Environment

```markdown
- OS: Windows 11, 24H2 (OS build 26100.7462)
- Other network-level software: None
```

### Which DNS server do you use?

Default

### Custom DNS

_No response_

### Use Wintun

- [ ] yes, I do

### Issue Details

Steps to reproduce:
1. Launch the app and login in a local session at higher resolution (like 2560x1440)
2. Place the window closer to the right edge of the screen
3. Logoff
4. Connect via RDP at lower resoltion (like 1440x900)

### Expected Behavior

The window should detect when its client area goes beyond screen size, where it becomes unusable, and position itself correctly (in a user-friendly way).

### Actual Behavior

The window placed itself beyond the visible screen aread, so it is hardly visible (refer to the screenshot, where some marginal case is presented).
Moreover the user can't interact with the welcome screen (to move it).
If you log on locally (without logging off from RDP session), you may discover that the app has aligned its main window just in the bottom right corner (why not centering?), so at even lower resolutions (like 1366x768) the user may not be able to see the window at all.

### Screenshots

Screenshot 1
The window is positioned at the right bottom corner of the screen, but mostly offscreen:

### Additional Information

Related issues:
* https://github.com/AdguardTeam/AdGuardVPNForWindows/issues/750
* https://github.com/AdguardTeam/AdGuardVPNForWindows/issues/752