Resolve a batch of email addresses to enriched contact records — the
same identity data as GET /api/v1/lookup, but up to 1000 emails per
call. Each email is normalized and SHA-256 hashed before lookup.

Filtering and billing. Provide an optional filter (same grammar as
the lookup endpoint) to receive only records that match; non-matching
records are dropped from the response and are not billed. Billing is on
egress as contact_record — only records that carry a business email
are billed, so a filtered-out or non-resolving email costs nothing. To
receive and be billed for only records with a current business email,
set filter to current_business_email:ne:"".

Pagination. page_size (default 100, max 1000) bounds the page; a
non-empty cursor in the response means more records remain — pass it
back to fetch the next page.