CLI billing and budget management commands

Features

• CLI billing and budget management commands
• CLI commands for agents, overrides, and attachments
• Contacts proxy in the agentic-mailbox service with matching CLI commands
• CLI-based agent skill reference — view the full API reference from your terminal

Fixes

• Thread message bodies now correctly decrypted on the read path
• Added missing mail-encryption, mail-observability, and mail-dmarc packages to Dockerfiles
• Fixed DMARC reports tenant_id type mismatch
• Fixed CLI package resolution issues