Mailbox management: delete, pause/resume, change email address, and clone mailboxes

Features

• Mailbox management: delete, pause/resume, change email address, and clone mailboxes
• Mailbox analytics: per-mailbox usage stats with 24h/7d/30d periods in portal
• CLI: add mailboxes delete, clone, and stats commands
• CLI: add --payload flag to send simulate for policy testing with real payloads
• CLI: rename threads followup argument from threadId to requestId
• Docs: expanded mailbox management documentation with API examples
• Blog: What's New post covering free tier, broadcast send, and mailbox control

Fixes

• CLI: suppress update notice when stderr is not a TTY (fixes piped output)
• Agentic mailbox: add missing safety-settings and humanizer proxy routes
• Docs: fix DogFood-reported issues in CLI quickstart, journeys, and suppressions docs