Add pre-send PII scanning for outbound emails

Problem
Front does not provide a pre-send warning or block when outbound emails contain personally identifiable information or sensitive attachments. Google's DLP service includes a "Warn Users" action that prompts senders before delivery, but this capability is not currently supported or surfaced in Front.

Request
Add native pre-send PII scanning and attachment blocking for outbound emails, or integrate with Google DLP's "Warn Users" feature so teammates are prompted before sending content that may violate data loss prevention policies.