Migrate service layer from AngularJS to React

[devin-ai-integration]

Migrate service layer from AngularJS to React

Summary

This PR implements the first phase of service layer migration from AngularJS to React, creating React equivalents of CommentService and AuthorService while maintaining full backward compatibility. React components now use React services via Context API instead of accessing Angular services through the bridge helper.

Key Changes:

• Created React CommentService and AuthorService classes using fetch API (same endpoints: localhost:3004/comments and localhost:3004/authors)
• Implemented ServiceProvider component using React 15's legacy Context API to provide services to React components
• Updated CommentList from functional to class component to consume services from context
• Modified reactToAngularComponent bridge to automatically wrap React components with ServiceProvider
• Removed unused render helper function

Architecture: React components now get services via Context API, while Angular components continue using Angular services via dependency injection. Both service layers coexist during the migration period.

Review & Testing Checklist for Human

• End-to-end functionality: Navigate to http://localhost:3000 and verify comments display with correct author names ("John Doe", "Eddart Stark")
• Backward compatibility: Verify existing Angular components still function (though only React components exist in this demo)
• Service timing: Check for race conditions - author data should load before CommentList renders (ServiceProvider has loading state)
• Error scenarios: Test with API server down (npm run api) to verify graceful degradation
• Context API stability: Verify services persist correctly across component re-renders and state changes

Test Plan:

1. Start API server: npm run api (port 3004)
2. Start dev server: npm start (port 3000)
3. Verify comments render with author names
4. Check browser console for errors
5. Test page refresh and navigation

Notes

• Uses React 15's legacy Context API (childContextTypes/contextTypes) since React.createContext was added in v16.3
• Services are singleton instances shared across all React components
• API endpoints remain unchanged for seamless migration
• All original Angular service files remain untouched

Link to Devin run: https://app.devin.ai/sessions/b1a8776083de4bf19288ddf6bcbeeda8
Requested by: @benc-a11y

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