feat: add frontend integration guide

[Mackenzie-OO7]

Cedra Builders Forge - Submission

Season 1

📋 Task Information

Task Title: Add a technical guide on how to integrate with frontend frameworks

Issue Link: #62

Telegram: @levai007

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✅ Checklist

• Commented "I'm taking this task" on the issue before starting
• This PR contains ONE task only
• All work is original (no copy-paste)
• Code compiles without errors and all tests pass
• Includes README, tests, and documentation
• Will share PR in Cedra Builders Telegram

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📝 What Was Built

This PR adds a comprehensive guide that demonstrates how to build a React application to interact with the Cedra counter smart contract.

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Pages Affected

New Page:

• [/docs/guides/counter-frontend.md - New frontend integration guide

Modified Pages:

• [/docs/real-world-guides.mdx] - Added card linking to the new frontend guide
• [sidebars.ts] - Added navigation entry under "Real World Guides" section

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📚 Documentation

• README with setup instructions
• Code comments on complex logic
• Working usage examples
• API documentation

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🎯 Quality Check

I confirm my submission:

• Handles edge cases and errors properly
• Follows Move conventions and best practices
• Is gas efficient and reusable
• Has clear structure and helpful error messages
• Does NOT contain plagiarism, malicious code, or spam

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📸 Demo (Optional)

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I have read and agree to follow all Cedra Builders Forge rules.

[Mackenzie-OO7]

@ya-dvorovenko i'm one of the winners of the builders forge, my tg handle is @levai007
thanks