OS Widgets v61

[ovitrif]

The calculator OS home-screen widget work is descoped from 2.3.0, aka OS Widgets Release, so the in-app calculator v61 work can be merged in time, considering the OS widget version of it needs redesign with consideration for the platform limitations we identified.

Widgets Platform Constraints

1. It is not possible to have dynamic UI outside OS widgets view on home screen, at best we need all the interact-able UI elements of the widget displayed from the start on it.
2. Keyboard, either the OS variant or the custom numpad styled by the app, cannot pop-up on click, nothing can be displayed outside the UI bounds of a widget, hard limitation on both platforms.
3. We could still have different UIs based on "media queries", updating the shape and functionality of the calculator, in conformance with the different permutations of widgets size, aka. the "grid", as described and demonstrated in the Android OS Widgets Sizes official design guide by Google's Android team: Getting Started, or the Figma Widget template examples.
4. Incompatibility of the widgets' current design in v61 wrt. the OS widget size requirements enforced by the "grid" on the OS home screen (synonymdev/bitkit-android#942:issuecomment-4477616284)

Backup branch preserving the extracted OS widget work:

• backup/calculator-os-widget-v61

Follow-up scope tbd post-release 2.3.0:

• Restore the calculator OS widget from the backup branch when design/product are ready.
• Decide whether the OS widget is display-only or opens Bitkit into the calculator flow.
• Keep OS widget state separate from in-app widget deletion if the OS widget returns.
• Recheck widget picker preview, Glance layout responsiveness, and locale-aware amount formatting.
• Add dedicated automated coverage in PRs restoring it, or their follow-ups.

Tasks

• feat: calculator v61 redesign #942
• test: add android test lanes #943
• fix: polish widgets foundation #952
• test: add calculator widget device tests #944