Create Email automation

selection_mode=mailing_list — recipients via uploaded emails or existing Lists (vault_files with non-empty creator_emails).

NOTE: lists referenced by lists_selected MUST contain at least one email address — the vault_files.creator_emails JSONB column must be non-empty. Targeting requires emails to send to. The route validates this at create time and returns 400 LIST_MISSING_EMAILS for any list that lacks emails. Per architecture review 2026-05-01.

selection_mode=filters — recipients via creator search filters. Subset of the saved_searches.filters JSONB shape — fields that make sense for email outreach. Backend translates this into the legacy filters JSON.

Outreach-paradigm recipient exclusion. Mirrors creators_to_omit in the legacy DB column / frontend payload, plus the boolean exclude_previously_messaged flag from the portal's Exclude Creators panel.

Email attachments — [{name, url}] shape. URL must be a hosted HTTPS URL (no file uploads). Server fetches at create time and re-hosts internally.

Canonical write-endpoint response. Replaces the v1 AutomationResource (which mirrored the legacy single-shape body). Now reflects the four-type taxonomy — automation_type is the public-API type, not the DB string. The DB string is in _internal_type for debugging only.