Feature: Celestia-backed NPM Registry

## Summary

Expose an npm-compatible registry API backed by Celestia blobs through Apex.

Example usage:

```
npm publish --registry=https://apex.dev/npm
npm install package-name
```

## Motivation

The npm ecosystem currently depends on centralized infrastructure.

Using Celestia DA would provide:

- Permanent package availability
- Censorship resistance
- Decentralized package distribution
- Verifiable package storage

## Architecture

```
npm client
↓
npm registry API
↓
SQLite metadata/index
↓
Apex blob client
↓
Celestia blobs
```

Package tarballs would be chunked and stored as blobs.

## Implementation Steps

1. Implement blob transaction submission in Apex
2. Store package tarballs as blobs
3. Store package metadata in SQLite
4. Expose npm registry compatible endpoints