Fix: Auth0-Lock Error with React 19 and Nextjs 15

[ankita10119]

Changes

Fixes React 19 and NextJS 15 compatibility issues in auth0-lock by removing deprecated APIs that were removed in React 19:

• Legacy string refs (ref="name")
• ReactDOM.findDOMNode()
• react-transition-group v2 (which used deprecated APIs)

Root Cause: auth0-lock was using legacy string refs (e.g., ref="chrome") which were removed in React 19

• Closes #2590

Changes Made

1. String Refs → React.createRef() (13 files)

Converted all legacy string refs to the modern createRef() pattern:

Before (React 18 and earlier):

<Chrome ref="chrome" />
this.refs.chrome.focusError()

After (React 19 compatible):

constructor(props) {
  super(props);
  this.chromeRef = React.createRef();
}
<Chrome ref={this.chromeRef} />
this.chromeRef.current.focusError()

2. Removed ReactDOM.findDOMNode() Replaced all ReactDOM.findDOMNode() calls with direct ref access:

Before:

const node = ReactDOM.findDOMNode(this);
node.focus();

After:

const node = this.nodeRef.current;
node.focus();

3. Added nodeRef Props to CSSTransition

Added nodeRef props to CSSTransition components to avoid react-transition-group's findDOMNode fallback:

Before:

<CSSTransition classNames="slide" timeout={350}>
  {children}
</CSSTransition>

After:

<CSSTransition
  nodeRef={this.transitionRef}
  classNames="slide"
  timeout={350}
>
  <div ref={this.transitionRef}>
    {children}
  </div>
</CSSTransition>

4. Dependency Upgrades

• React: 18.2.0 → 19.2.1
• React DOM: 18.2.0 → 19.2.1
• react-transition-group: 2.2.1 → 4.4.5 (v2 used deprecated React APIs)

Testing

Test Environment:

• Next.js 15.2.6
• React 19.2.1
• React DOM 19.2.1

Test Scenarios:

• Lock widget renders without errors
• No "Expected ref to be a function" errors
• No "findDOMNode is not a function" errors
• No legacy context API warnings
• Widget interactions work (typing, tab switching, form submission)

• [ ] This change adds unit test coverage
• [ ] This change adds integration test coverage
• [ ] This change has been tested on the latest version of the platform/language

Checklist

• [x] I have read the Auth0 general contribution guidelines
• [x] I have read the Auth0 Code of Conduct
• [x] All code quality tools/guidelines have been run/followed
• [ ] All relevant assets have been compiled