Add repo cloning to sandboxes and providers
Add a clone(repoUrl) API to BaseSandbox and implement it for
Daytona, Deno, Vercel, Sprite and Cloudflare. Trigger a git clone
during sandbox start when a repo is set (apps/sandbox and
apps/cf-sandbox). Also implement mkdir, writeFile and setupSshKeys
for Daytona, Deno and Vercel, import path where needed, and tidy up
some command returns and permission handling.