Country code search is case sensitive

### 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

2.7

### Operating mode

Integration with AdGuard

### Which DNS server do you use?

Custom DNS

### DNS protocol

DNS-over-HTTPS

### Custom DNS

_No response_

### Environment

```markdown
- OS: Android 14
- Device: pixel 6a
```

### Root access

- [ ] yes, I have it

### Issue Details

Steps to reproduce:
1. Open locations search
2. Type `tr` or `Tr`

Also probably incorrect behavior - when entered `T` the app shows mixed results - locations with `t` letter in the name + `Turkey`

### Expected Behavior

Turkey should be displayed.
When entered `TR`, Turkey is displayed.

The country code search should be performed when two characters are entered, regardless of case. If entered one or more than two characters, apply a regular search.

### Actual Behavior

No results.

### Screenshots

_No response_

### Additional Information

_No response_