Mx-A: Numeric filter predicates on GET /api/v1/utilities

Add min_customers, max_customers, min_ami_meters, min_total_meters, has_logo, has_website, has_territory filters to the existing utilities list endpoint. Unblocks Atlas Phase 2 list views. Spec reference: TextureHQ/mono specs/relay/commongrid-nisc-matcher.md v1.5 (pending). Public-useful (any consumer wants these).