Write: NEAR Account Model Deep Dive

Description

## Overview
Write a comprehensive guide explaining NEAR's unique account model - named accounts, access keys, and permissions.

## Why This Matters
NEAR's account model is powerful but different. Clear explanation accelerates developer understanding.

## Content Requirements
- Named vs implicit accounts
- Access key types and permissions
- Multi-sig patterns
- Account creation flows
- Security best practices

## Deliverables
1. Comprehensive guide (3000+ words)
2. Diagrams and examples
3. Code snippets
4. Published to dev portal