fix(android): apply modern system bar appearance on Android 12+

[huxinhai]

Closes #80

What changed

• Use the platform WindowInsetsController.setSystemBarsAppearance API on Android 12+.
• Preserve the existing WindowInsetsControllerCompat path on Android 11 and below.
• Keep status, navigation, and both isolated through their respective appearance masks.

Why

On an affected Xiaomi Android 12 device, the window-backed compat controller could report light status-bar appearance as enabled while only the legacy systemUiVisibility flag had changed. SystemUI continued to consume the modern WindowManager appearance, so the status-bar icons returned to white after task removal and process restoration.

Calling the platform controller directly on API 31+ matches React Native's current Android status-bar implementation and updates the modern appearance consumed by SystemUI. There are no JavaScript API or default-value changes.

User impact

Apps using setBarStyle('dark', 'status') no longer lose dark status-bar icons during affected OEM task/process transitions.

Validation

• Node 24.13.0 / Yarn 4.11.0
• yarn install --immutable
• yarn typecheck
• yarn lint
• yarn test — 2 suites, 44 tests
• yarn prepare
• :react-native-system-navigation-bar:compileDebugKotlin --rerun-tasks in the example app
• :react-native-system-navigation-bar:assembleDebug in the example app
• Downstream React Native 0.85 DogRelease build and install
• Xiaomi Mi 10S, Android 12 / API 31: remove from recents, reopen, and process-restoration checks retained apr=LIGHT_STATUS_BARS; no Android or React Native fatal logs

The issue did not reproduce on the Android emulator; the before/after WindowManager evidence was captured on the physical Xiaomi device.