Build LangChain Tool: NEAR Price & Market Data

Description

## Overview
Create a LangChain tool that provides real-time NEAR price data, market metrics, and historical trends for agent applications.

## Why This Matters
Agents need market data to make informed decisions. This tool provides reliable price feeds.

## Technical Requirements
- Real-time NEAR price from multiple sources
- Historical price data
- Market cap and volume
- Price alerts capability
- Support for NEAR ecosystem tokens

## Deliverables
1. PyPI package: langchain-near-price
2. Multiple data source aggregation
3. Caching for rate limits
4. Documentation with examples