Create VS Code extension for Prax schema

## Description
VS Code extension for .prax schema files with syntax highlighting, autocomplete, and validation.

## Features
- [ ] Syntax highlighting
- [ ] Autocomplete for types, attributes
- [ ] Inline validation errors
- [ ] Go to definition
- [ ] Hover documentation
- [ ] Format on save
- [ ] Schema visualization

## Related
Similar to Prisma VS Code extension