Build GitHub Action: NEAR Contract Size Check

Description

## Overview
Create a GitHub Action that checks NEAR contract WASM size and warns if approaching limits.

## Why This Matters
NEAR has contract size limits. Catching size issues in CI prevents deployment failures.

## Technical Requirements
- Build contract WASM
- Check size against limits
- Compare with previous builds
- Suggest optimizations
- Fail if over limit

## Deliverables
1. GitHub Action on Marketplace
2. Size comparison
3. Optimization suggestions
4. Clear warnings