> [!IMPORTANT]
> This PR is all dark code, nothing is used yet. PR 5 will wire it all
together


This PR is prepping for color extraction and paywall styling. Unused
code.

## Summary
- Adds ColorComputationHelpers with WCAG 2.0 contrast ratio and
luminance calculations
- Adds AppStyleExtractor to extract app name, icon bitmap, and prominent
colors from the app icon at runtime
- Adds CircleOutlined vector icon for unselected product cells
- Includes tests for color extraction, contrast computation, and
luminance

Part 2 of the fallback paywall feature breaking up #2945. Stacked on
#3131.

- Add PaywallWarning type for fallback paywall #3131 
- Add color helpers, AppStyleExtractor, and CircleOutlined icon #3132
(This PR)
- Add default paywall UI components #3133
- Wire validation warning through paywall state pipeline #3134
- Plug in Paywall
- Remove Big background image and clean up CI



<!-- CURSOR_SUMMARY -->
---

> [!NOTE]
> **Low Risk**
> Adds new, currently-unused helper utilities and a vector icon with
unit tests; no changes to runtime paywall flow or persisted data.
> 
> **Overview**
> Prepares groundwork for styling by adding `AppStyleExtractor` to fetch
app name/icon and to asynchronously extract a small set of prominent
colors from a bitmap via sampling, quantization, and
similarity/brightness/alpha filtering.
> 
> Introduces `ColorComputationHelpers` with WCAG-based
luminance/contrast utilities (plus best-contrast selection) and adds a
new `CircleOutlined` Compose `ImageVector`.
> 
> Adds Robolectric tests covering prominent-color extraction edge cases
and the new color math helpers (distance, luminance, contrast, and
selection).
> 
> <sup>Written by [Cursor
Bugbot](https://cursor.com/dashboard?tab=bugbot) for commit
3619218. This will update automatically
on new commits. Configure
[here](https://cursor.com/dashboard?tab=bugbot).</sup>
<!-- /CURSOR_SUMMARY -->

---------

Co-authored-by: Claude Opus 4.6 <noreply@anthropic.com>

<!-- Thank you for contributing to Purchases! Before pressing the
"Create Pull Request" button, please provide the following: -->


Wires in the default paywall into the sdk for use. Adds previews for
emerge snapshot testing

Part 5 of the fallback paywall feature breaking up
#2945. Stacked on
#3134

- Add PaywallWarning type for fallback paywall
#3131
- Add color helpers, AppStyleExtractor, and CircleOutlined icon
#3132
- Add default paywall UI components
#3133
- Wire validation warning through paywall state pipeline
#3134
- Plug in Paywall
#3178 (This PR)
- Remove Big background image and clean up CI

<!-- CURSOR_SUMMARY -->
---

> [!NOTE]
> **Medium Risk**
> Introduces a new paywall rendering path that can trigger
purchase/restore actions from the fallback UI, so regressions could
affect paywall display and transaction initiation when validation
warnings occur.
> 
> **Overview**
> Adds a *fallback “default paywall”* flow: `InternalPaywall` now
renders `DefaultPaywallView` whenever a legacy paywall loads with a
`validationWarning`, wiring its purchase/restore actions through the
existing `PaywallViewModel` and reusing a shared `screenModeBackground`
modifier.
> 
> Refactors `DefaultPaywallView` layout to use `Scaffold` with a fixed
footer and `LazyColumn`, adds preview-only overrides plus new Compose
previews, and introduces a deterministic `DualColorImageGenerator` used
by previews and a new `AppStyleExtractor` prominent-colors test. Also
removes developer-facing debug strings from `strings.xml` in favor of
local constants, and updates `.gitignore` to exclude `.cursor/`.
> 
> <sup>Written by [Cursor
Bugbot](https://cursor.com/dashboard?tab=bugbot) for commit
42d3af2. This will update automatically
on new commits. Configure
[here](https://cursor.com/dashboard?tab=bugbot).</sup>
<!-- /CURSOR_SUMMARY -->

## Summary
- Adds validationWarning: PaywallWarning? field to
PaywallState.Loaded.Legacy
- Threads validationWarning through
OfferingToStateMapper.toLegacyPaywallState
- Passes validationResult.warning from PaywallViewModel.calculateState
to the state mapper

When a paywall fails validation, the warning is now carried on the
loaded state, ready for the UI layer (PR 5) to check and render the
DefaultPaywallView instead of the template paywall.

Part 4 of the fallback paywall feature breaking up #2945. Stacked on
#3133.

- Add PaywallWarning type for fallback paywall #3131 
- Add color helpers, AppStyleExtractor, and CircleOutlined icon #3132
- Add default paywall UI components #3133
- Wire validation warning through paywall state pipeline #3134 (This PR)
- Plug in Paywall #3178
- Remove Big background image and clean up CI


<!-- CURSOR_SUMMARY -->
---

> [!NOTE]
> **Low Risk**
> Low risk additive change: it only carries an optional `PaywallWarning`
through state creation and does not alter validation or rendering logic
yet.
> 
> **Overview**
> **Threads paywall validation warnings through the Legacy paywall
state.** `PaywallState.Loaded.Legacy` now includes an optional
`validationWarning: PaywallWarning?`.
> 
> `PaywallViewModel.calculateState` passes `validationResult.warning`
into `Offering.toLegacyPaywallState`, and the mapper stores it on the
created legacy state so the UI can later decide to show a
fallback/default paywall when validation issues occur.
> 
> <sup>Written by [Cursor
Bugbot](https://cursor.com/dashboard?tab=bugbot) for commit
64f72f8. This will update automatically
on new commits. Configure
[here](https://cursor.com/dashboard?tab=bugbot).</sup>
<!-- /CURSOR_SUMMARY -->

---------

Co-authored-by: Claude Opus 4.6 <noreply@anthropic.com>

## Summary
- Adds DefaultPaywallView composable: the main fallback paywall with
dynamic app icon theming, package list, purchase and restore buttons
- Adds DefaultPaywallWarning: debug-only warning panel showing what went
wrong, with RevenueCat branding and dashboard links
- Adds DefaultProductCell: selectable product row with animated color
transitions
- Adds RevenueCat branding image and string resources for the default
paywall

Part 3 of the fallback paywall feature breaking up #2945. Stacked on
#3132.

- Add PaywallWarning type for fallback paywall #3131 
- Add color helpers, AppStyleExtractor, and CircleOutlined icon #3132
- Add default paywall UI components #3133 (This PR)
- Wire validation warning through paywall state pipeline #3134
- Plug in Paywall #3178
- Remove Big background image and clean up CI



<!-- CURSOR_SUMMARY -->
---

> [!NOTE]
> **Medium Risk**
> Adds a new fallback paywall UI path for legacy paywalls and threads a
new `validationWarning` through state mapping, which can change what
users see when paywall validation fails (though warning UI is
debug-only). Main risk is UI/behavior regressions around package
selection, purchase/restore entrypoints, and full-screen vs sheet
background handling.
> 
> **Overview**
> Adds a new **default/fallback paywall** Compose UI
(`DefaultPaywallView`) that themes itself from the app icon, shows a
selectable package list, and provides localized *Purchase*/*Restore*
actions, plus a debug-only `DefaultPaywallWarning` panel (with a
Dashboard link) and preview/test utilities.
> 
> Wires a new `validationWarning: PaywallWarning?` through
`PaywallValidationResult` mapping into `PaywallState.Loaded.Legacy`, and
updates `InternalPaywall` to render the new default paywall when the
warning is present (including refactoring background handling via
`screenModeBackground`).
> 
> Updates test/mocks to support the new legacy fallback flow (selection
mutates state; purchase captures selected package id; restore uses
`restorePurchases()` entrypoint) and adds string resources for the
default paywall across locales; also ignores `.cursor/` in `.gitignore`.
> 
> <sup>Written by [Cursor
Bugbot](https://cursor.com/dashboard?tab=bugbot) for commit
6ca1786. This will update automatically
on new commits. Configure
[here](https://cursor.com/dashboard?tab=bugbot).</sup>
<!-- /CURSOR_SUMMARY -->

---------

Co-authored-by: Claude Opus 4.6 <noreply@anthropic.com>