fix(react): convert GooglePayButton to functional component for React 19 compatibility

[hanumanteshvar07-design]

This PR resolves the compatibility issue with React 19 where accessing .ref on a React element was deprecated and now throws a warning/error.

By converting GooglePayButton to a functional component using React.forwardRef, we align with modern React patterns and ensure that ref is handled correctly as a prop, avoiding the legacy class-component behavior that triggers React 19 warnings.

Changes:

src/button-react/GooglePayButton.tsx: Converted to a functional component with React.forwardRef.
src/button-react/GooglePayButton.test.tsx: Updated to support both legacy ReactDOM.render and the modern createRoot API.
src/button-react/GooglePayButton.react19.test.tsx: Enhanced to include regression tests for React 19 ref access patterns.
Formatting: Normalized codebase formatting using Prettier to satisfy linting rules.

Verification:

All 49 tests passed (including core logic, web component, and React components).
Verified compatibility with both React 16 and React 19 environments.
npm run lint passes successfully.

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