[BUG] Avalonia: UI state mismatch for upgradable packages/apps selection

### Please confirm these before moving forward

- [x] I have searched for my issue and have not found a work-in-progress/duplicate/resolved issue.
- [x] I have tested that this issue has not been fixed in the latest [(beta or stable) release](https://github.com/Devolutions/UniGetUI/releases/).
- [x] I have checked the [FAQ](https://github.com/Devolutions/UniGetUI#frequently-asked-questions) section for solutions.
- [x] This issue is about a bug (if it is not, please use the [correct template](https://github.com/Devolutions/UniGetUI/issues/new/choose)).

### UniGetUI Version

v2026.1.10

### Windows version, edition, and architecture

Windows 11 Pro 26200.8457 x64

### Describe your issue

Just like mentioned in the **resolved** #4009, where this bug was observed initially (*classic mode* now), it seems the bug has crawled into the Avalonia version as well.

Upon launch, UniGetUI shows that the upgradable packages/apps are selected, yet they are **not**, see screenshot below.

### Steps to reproduce the issue

1. Disable classic mode in the Settings (= use Avalonia)
2. Notice that UI/state mismatch

### UniGetUI Log

```text
N/A
```

### Package Managers Logs

```text
N/A
```

### Relevant information

_No response_

### Screenshots and videos

_No response_