Find Similar Job Roles

Soft duplicate-detection at create time. Returns up to 3 active roles in the same org whose titles overlap with title. Used by the create-role form to surface a non-blocking "similar role exists" banner so recruiters don't fragment the candidate pipeline by accidentally creating "Sr PD" and "Senior Product Designer" as separate roles.

Matching is intentionally simple (case-insensitive substring in either direction, plus exact match). Doesn't catch abbreviation differences like "Sr" vs "Senior" — fuzzy matching via pg_trgm is a future iteration once we see real-world false negatives.