spp_api_v2_programs: program references are name slugs resolved with =ilike + limit=1 — hyphenated names never resolve, case variants can resolve to the wrong program

[gonzalesedwin1123]

Problem

Program references are built as Program/urn:openspp:program|<name lowercased, spaces → ->
(ProgramMembershipService._build_program_reference), and resolved by reversing the slug
(ProgramService.find_by_identifier: value.replace("-", " "), name =ilike, limit=1). The spp.program.id
model the code checks for does not exist in this repo, so the slug path is always used.

• A program whose name contains a hyphen never round-trips, so its reference returns 404 on
  ?program= / POST / PUT ("Cash-Plus" → slug cash-plus → searched as "cash plus").
• Program-name uniqueness is case-sensitive, so "Cash Transfer" and "CASH TRANSFER" can coexist; both slug to
  cash-transfer and =ilike + limit=1 picks one. Since PR fix(api_v2): REST API v2 defects found by the OpenFn adaptor (#554) #555, ?program= selects which membership a
  GET/PUT /ProgramMembership acts on, so a wrong resolution updates the wrong program's membership (the PUT
  identity guard passes because the body resolves to the same wrong program).

Proposal

Give programs a stable external identifier (e.g. a program code / spp.program.id), use it in references, and resolve
exactly (409 on multiple matches). Keep slug resolution only as a deprecated fallback, refusing ambiguity.

Context

Found in the adversarial review of PR #555 (#554); pre-existing, but load-bearing since ?program=.