Protected Quick Tunnels: simple accountless authentication for your next dev project

Introduced email-based authentication for Quick Tunnels via the `--allowed-mail` flag in `cloudflared` and `wrangler tunnel quick-start`. This feature leverages Cloudflare Access for email verification and a stateless authentication broker on Workers to issue signed assertions, which `cloudflared` then uses for authorization against locally stored rules. This enables accountless, protected ephemeral tunnels for agentic workflows and local development previews.