Reusable RQL → SQL query-building helpers

Reusable RQL → SQL query-building helpers: a task in MiMo-V2.6-RL-harbor-code: MiMo-V2.6-RL Code (Harbor) (Harbor dataset). We're adding RQL-driven listing (filtering, full-text search, pagination and grouping) to several admin list endpoints, starting with prospects. Rather than hand-roll the SQL…