fix(android): clear focus and hide the keyboard when leaving a page

[KisaneNeko]

Summary

Fixes #1154. Reported in Expensify/App#101157 after bumping from 8.0.0 to 9.0.4.

On Android, a focused TextInput keeps focus after its page is left with setPage or a swipe. The keyboard stays open with nothing focused on screen, and typing still goes into the input on the page you just left.

reproduction

Before (9.0.6)	After (this PR)
1154-before-9.0.6.mp4	1154-after-fix.mp4

What happened

• v8 used ViewPager2, which clears focus on every page change. The keyboard also closed, but only because ViewPager2's RecyclerView detached the off-screen page.
• v9 moved to Compose HorizontalPager. It doesn't touch focus, and neighbouring pages stay attached, so the input keeps both focus and the keyboard.

Fix

When a page is selected, ComposePagerView now clears focus held outside that page, and hides the keyboard if it was attached to the input that lost focus.

• Focus inside the selected page is left alone, so an input focused right after setPage (while the pager is still animating) keeps it. ViewPager2 cleared that one too.
• The keyboard is hidden manually because the old page is no longer detached.
• One trade-off: if an app focuses an input from onPageSelected, the keyboard hides and then shows again.

Test Plan

What's required for testing (prerequisites)?

Android emulator or device. A pager with a TextInput on at least two pages.

What are the steps to reproduce (after prerequisites)?

Added Issue #1154 Page Change Focus Repro to the example app and .maestro/android-only/issue_1154_page_change_focus_repro.yaml:

1. Open the example, tap Go 1 and focus the input on page 1.
2. Tap Go 0, or swipe to another page.
3. Before: the keyboard stays open, nothing on page 0 is focused, and typing goes into page 1's input.
4. After: the input is blurred and the keyboard closes.
5. The onSelected / onPress buttons focus the new page's input from onPageSelected or right after setPage. Both still end with that input focused.

Verified

• typescript, lint (no new warnings) and test pass, plus the Android unit tests.
• The new Maestro flow fails on 9.0.6 and passes with the fix (Pixel 4 emulator, API 34, debug build).
• Full Android Maestro suite with the fix: 12/13 pass. issue_1096_keyboard_shrink_repro fails the same way without the fix (the keyboard covers the row it taps). pager_vertical_basic_example and issue_1083_modal_set_page_repro failed on the first run and passed on a rerun, with and without the fix.
• Checked against Expensify's Split screen pattern (material top tabs, tab press, delayed auto-focus) in a scratch screen: the hidden input no longer takes input, and their auto-focus still works.

iOS is untouched.

Compatibility

OS	Implemented
iOS	n/a
Android	✅

Checklist

• I have tested this on a device and a simulator: emulator only (Pixel 4, API 34), not on physical hardware
• I added the documentation in README.md: not applicable
• I updated the typed files (TS and Flow): not applicable