Write: NEAR Security Best Practices

Description

## Overview
Create a security guide for NEAR smart contract developers - common vulnerabilities and how to avoid them.

## Why This Matters
Security knowledge prevents hacks. A clear guide helps developers build safely.

## Content

### Topics
- Access control patterns
- Input validation
- Storage attacks
- Callback security
- Upgrade safety
- Audit checklist

## Deliverables
1. **Security guide** - 5000+ words
2. **Vulnerability examples**
3. **Prevention patterns**
4. **Audit checklist**

## Budget: 6 NEAR