docs(apps/guides): add build-mini-app-with-token-rewards guide

[consumeobeydie]

Summary

Adds a new guide to docs/apps/guides that shows developers how to build a Farcaster Mini App on Base that rewards users with ERC-20 tokens for on-chain interactions.

Motivation

There is currently no guide in the Base docs covering the pattern of combining ERC-20 token rewards with Mini App interactions. This is one of the most common incentive patterns for Base Mini Apps, and developers currently have to piece together multiple guides to implement it.

What's covered

• Designing a combined ERC-20 token + reward logic smart contract (single contract pattern)
• Deploying to Base mainnet using Remix IDE
• Building a Mini App frontend with wallet support for both Base App (embedded wallet) and MetaMask
• Configuring the Farcaster manifest and generating accountAssociation
• Registering on Base App and obtaining a base:app_id
• Deploying to Vercel with automatic CI/CD

Live Example

The guide references a fully working implementation built on Base mainnet:

• App: https://base-bookvs-movie.vercel.app
• Contract: 0x407EacD1aAF2F46cC4079BFC4bef0c197A1FD6A8 (Base Mainnet)
• GitHub: https://github.com/consumeobeydie/BaseBookvsMovie

Checklist

• New .mdx file added to docs/apps/guides/
• Follows existing guide format and tone
• Includes working code examples
• References a live deployed example

[cb-heimdall]

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