fix: polish widget foundation

[ovitrif]

Fixes #936
Supersedes #946

This PR restores the widget foundation polish from #946 as a standalone branch targeting master.

Description

This PR:

1. Shows the wide in-app widget preview by default and hides small preview variants that cannot be added yet.
2. Aligns widget preview and configuration screens with the shared Bitkit screen background and edge-to-edge system bar styling.
3. Makes the Facts OS widget open Bitkit when tapped.
4. Enables Android's OS widget reconfigure affordance for Price, Headlines, Blocks, and Weather.
5. Fixes the Price widget formatter so stored price text does not duplicate the currency symbol rendered by the widget UI.

Preview

Walkthrough	Widget OS Settings
scrcpy.2026-05-18.005832.mp4	scrcpy.2026-05-18.005833.mp4

QA Notes

Manual Tests

• 1. Home -> Widgets -> Add Widget: widget previews open on the wide preview and do not expose unavailable small variants.
• 2. Android launcher -> add Facts widget -> tap widget: Bitkit opens.
• 3a. Android launcher -> long-press Price widget -> Widget settings: Bitkit widget config opens.
  • 3b. Android launcher -> long-press Headlines, Blocks, and Weather widgets -> Widget settings: Bitkit widget config opens.
• 4. Widget config -> open Price, Headlines, Blocks, or Weather config: system bars match Bitkit edge-to-edge styling.
• 5. Android launcher -> view Price widget in a non-US locale: price text does not duplicate the currency symbol.

Automated Checks

• ./gradlew testDevDebugUnitTest --tests to.bitkit.data.widgets.PriceServiceTest
• git diff origin/master..HEAD --check