Add screen reader support for country select box

[rezabakhshilaktasaraei]

Summary

Exposes painted country rows in the country select box as virtual accessibility children, making the list navigable by screen readers.

Changes (country_select_box.cpp)

• Overrides accessibilityChildCount(), accessibilityChildName(), accessibilityChildRect(), accessibilityChildState(), and accessibilityChildRole() on the inner widget.
• Each country row becomes a ListItem accessible child.
• In phone mode, the name combines country name + dial code (e.g. "Iran, +98").
• In non-phone mode, only the country name is used.
• Fires accessibilityChildFocused() when selection changes via keyboard.
• Announces selected row on focusInEvent.

Dependencies

• Requires lib_ui#278 for Accessible::Item infrastructure.

No new lang keys

Uses only existing lng_country_* keys — no new strings added.

Test plan

• Open country selector (phone registration or settings) with a screen reader
• Navigate rows with arrow keys — screen reader announces country name (and dial code in phone mode)
• Verify hit-testing: clicking a row with screen reader cursor selects the correct country