Add "Read data with Farcaster Auth" guide

[VolodymyrBg]

This PR adds a new guide that shows how to read data from the Farcaster network after authenticating a user with Farcaster Auth. The guide includes:

• Setting up a React application with Farcaster Auth Kit
• Authenticating users with the SignInButton component
• Displaying user profile information after authentication
• Fetching and displaying the user's recent casts from a Farcaster Hub

This implementation resolves one of the TODO items in the documentation navigation.

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PR-Codex overview

This PR focuses on adding a new guide for reading data with Farcaster Auth, enhancing the documentation and providing a detailed tutorial for creating a React application that authenticates users and fetches their profile information and recent casts.

Detailed summary

• Updated docs/.vitepress/config.mts to include a link to the new guide.
• Created docs/developers/guides/apps/read-with-auth.md with:
  • Introduction to reading data with Farcaster Auth.
  • Prerequisites for setting up the application.
  • Step-by-step instructions for creating a React app.
  • Code examples for App.jsx and UserCasts.jsx components.
  • Explanation of how the application works and next steps for enhancements.

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