feat: add secure-wallet-persistence-agentkit tutorial

[jadonamite]

Summary

Adds a guide on securely managing AgentKit wallet persistence using AES-256-GCM encryption and atomic file operations.

Content

• Author: @jadonamite
• Stack: Node.js Crypto, AgentKit.
• Key Features:
  • WalletManager class implementation.
  • Encryption/Decryption logic for cdpWalletData.
  • Atomic write pattern to prevent file corruption during restarts.
  • Preparation for database integration.

Motivation

Standard tutorials use plaintext wallet_data.txt, which is insecure and prone to corruption. This guide provides a production-grade pattern for developers moving beyond "Hello World".

Verification

• Verified wallet creation and encryption.
• Verified wallet loading and decryption with correct key.
• Verified decryption fails gracefully with incorrect key.

[cb-heimdall]

🟡 Heimdall Review Status

Requirement	Status	More Info
Reviews	🟡 0/1	Denominator calculation Show calculation 1 if user is bot 0 1 if user is external 0 2 if repo is sensitive 0 From .codeflow.yml 1 Additional review requirements Show calculation Max 0 0 From CODEOWNERS 0 Global minimum 0 Max 1 1 1 if commit is unverified 0 Sum 1