fix(shadow*): replace depracated shadow props with boxShadow

[ozgegurel]

Issue: Deprecated shadow* Style Props in @storybook/ondevice-controls

Using the old (shadow*) props now triggers deprecation warnings in the console, which can clutter logs and may eventually lead to broken or unsupported styles in future React Native releases.

What I did

• Replaced deprecated React Native shadow style properties (shadow*) with the modern boxShadow property
• Updated styling in color picker components to use the new boxShadow syntax
• Fixed deprecation warnings in the codebase

How to test

1. Install dependencies and build the packages from the root directory:

   yarn install
   yarn build

2. Navigate to the example app and run it on iOS:

   cd examples/expo-example
   yarn ios

3. Open the color picker from Color Example on ios and verify that shadows are rendered correctly.
4. Confirm that no shadow-related deprecation warnings appear in the console.

Does this need a new example in examples/expo-example?

No, the changes are internal styling updates that don't require new examples.

Does this need an update to the documentation?

No, this is a technical implementation change that doesn't affect the public API or usage patterns.

Additional Notes

• This change follows React Native's current styling best practices
• The fix is backward compatible and doesn't introduce any breaking changes
• The update improves code quality by removing deprecation warnings

[dannyhw]

Thanks for the pr! LGTM