feat: adds preferred provider to ramp controller state

[georgeweiler]

Explanation

The RampsController has no mechanism to store a user's preferred ramp provider. This PR adds preferredProvider state to the RampsController.

1. Type Definitions: Added Provider, ProviderLink, and ProviderLogos types in RampsService.ts to match the API provider structure
2. State Management:
   • Added preferredProvider: Provider | null to RampsControllerState
   • Added metadata configuration (persist, includeInDebugSnapshot, includeInStateLogs, usedInUi)
   • Added preferredProvider: null to default state
3. API: Added setPreferredProvider(provider: Provider | null) method to update the state
4. Selectors: Added selectPreferredProvider selector in the mobile app for Redux access
5. Exports: Exported Provider, ProviderLink, and ProviderLogos types from the package index

The implementation follows the exact same pattern as userRegion, ensuring consistency and maintainability.

**Usage:**ript
// Set preferred provider
Engine.context.RampsController.setPreferredProvider(providerObject);

// Get preferred provider
const provider = Engine.context.RampsController.state.preferredProvider;
// Or via selector
const provider = useSelector(selectPreferredProvider);

References

https://consensyssoftware.atlassian.net/browse/TRAM-3150

Checklist

• I've updated the test suite for new or updated code as appropriate
• I've updated documentation (JSDoc, Markdown, etc.) for new or updated code as appropriate
• I've communicated my changes to consumers by updating changelogs for packages I've changed
• I've introduced breaking changes in this PR and have prepared draft pull requests for clients and consumer packages to resolve them

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Note

Introduces persisted provider preference in the ramps controller state.

• Adds preferredProvider to RampsController state (persisted, included in debug/state logs, exposed to UI) and defaulted to null
• Implements setPreferredProvider(provider: Provider | null) to update the state
• Defines Provider, ProviderLink, and ProviderLogos types in RampsService and exports them via index.ts
• Updates tests and snapshots for new state; adds unit tests for setPreferredProvider; adjusts selector tests to include preferredProvider
• Updates CHANGELOG.md to document the addition

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