[FEATURE] Implement cx new project template scaffolding

[mikejmorgan-ai]

Summary

The cx new command currently has a stub implementation that prints "not yet implemented". This needs full implementation to scaffold project templates.

Current State

// new.rs - stub only
println!("cx new: Project templates not yet implemented");

Required Templates

Template	Files Created
python	pyproject.toml, venv, src/init.py
rust	Cargo.toml, src/main.rs
node	package.json, index.js
react	package.json, src/App.tsx, vite config
nextjs	package.json, app/, next.config.js
fastapi	pyproject.toml, app/main.py, requirements.txt
go	go.mod, main.go
docker	Dockerfile, docker-compose.yml

Implementation Details

• Templates stored in ~/.cx/templates/ or bundled in binary
• cx new <template> <name> creates <name>/ directory
• cx new --list shows available templates
• Smart defaults based on current directory context

Acceptance Criteria

• All 8 templates implemented
• Each creates valid, runnable project
• Unit tests for template generation
• Integration with cx ask "create X project" pattern matching
• BSL 1.1 header in source files