What changed

Added a new home-screen widget that lets you switch your AirPods' listening mode — Off, ANC, Transparency, or Adaptive — directly from the home screen without opening the app. The widget adapts its layout to the size you pick:

• 1×1: four icons in the corners with a + divider
• 2×1 / 1×2: compact icon strip or column with per-cell dividers
• 2×2: grid with icon-only buttons
• wide / tall with labels: labeled pills that share space evenly

The configuration screen now previews the actual widget layout you'll see (ANC or battery), shows a hint that the widget can be resized, and guards against confirming with a profile that no longer exists or no longer supports ANC.

Closes #518

Technical Context

• The ANC widget ViewModel was consolidated into the existing WidgetConfigurationViewModel — widget type is detected at runtime via AppWidgetManager.getAppWidgetInfo(...) and exposed on the state so the single activity can drive both widgets. Profile list is filtered to ANC-capable devices when the widget type is ANC.
• Active-button styling uses Material3 colorSecondaryContainer / colorOnSecondaryContainer resolved from the app's Material3 DynamicColors theme. This gives guaranteed contrast regardless of the user's chosen widget background, after earlier attempts with tertiary / primary tints were not visible enough against custom themes.
• Icon drawables were aligned with the in-app AncModeSelector (DoNotDisturbOn, Headphones, Hearing, AutoAwesome) so the widget and the app show the same glyph for each mode.
• The AapCommand.SetAncMode path is the same one the in-app UI already uses — the widget goes through AapConnectionManager.sendCommand(...), which is already debounced and queued by the session engine, so no additional rate-limiting is needed in the widget callback.
• Widget picker has both a Glance providePreview() (for launchers that honor it, with localized mode labels) and a static anc_widget_preview_layout.xml fallback (for launchers that don't).
• minWidth / minHeight are 40dp so the widget can be resized to single-cell dimensions; the layout picker uses getCellsForSize to switch between the six variants.