docs(tutorial): Bitcoin Logic - Integrating sBTC Deposits

[jadonamite]

Description

This PR adds Module 27: sBTC Integration by @jadonamite. It explains the workflow for handling sBTC deposits in custom DeFi contracts.

Content Overview

• The Mint Flow: How BTC L1 transactions translate to SIP-010 mint events.
• Contract Logic: Implementing a deposit registry compatible with sBTC transfers.
• Frontend Logic: Generating the OP_RETURN payload for the Bitcoin transaction.

Checklist

• Distinction between "Peg-in" and "Transfer" flows explained.
• Security warning regarding dynamic Gatekeeper addresses included.
• Formatting follows the repository's style guide.

Related Issues

Closes # (If applicable)

[cb-heimdall]

🟡 Heimdall Review Status

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