fix: refresh widgets after idle

[ovitrif]

Motivation

• Android home-screen widgets could show stale data after the device stayed idle because periodic WorkManager refreshes are deferred by the OS and there was no catch-up on unlock or idle-exit.

Description

• Add AppWidgetRefreshReceiver that enqueues a one-shot widget catch-up when Intent.ACTION_USER_PRESENT or PowerManager.ACTION_DEVICE_IDLE_MODE_CHANGED (idle exit) occurs.
• Add enqueueCatchUp one-time WorkManager path to AppWidgetRefreshWorker and hasActiveWidgets/cancel logic so catch-up runs only when OS widgets are installed and the catch-up work is cancelled when no widgets remain.
• Register the receiver at app startup (App.registerAppWidgetRefreshReceiver) and trigger the same catch-up when the app returns to foreground (AppWidgetRefreshWorker.enqueueCatchUp(context) in ContentView ON_START handler).
• Add Context.powerManager extension and a changelog fragment changelog.d/next/os-widget-idle.fixed.md describing the user-facing fix.

Testing

• git diff --check was run and produced no whitespace errors.
• Attempted ./gradlew compileDevDebugKotlin, ./gradlew testDevDebugUnitTest, and ./gradlew detekt, but they failed to run in this environment due to inability to resolve the Gradle plugin org.gradle.toolchains.foojay-resolver-convention:1.0.0 from configured repositories.
• No unit or detekt results were produced because of the plugin resolution failure.

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Codex Task