Migrate idle checker CRUD to ops-backed actions and the ProcessorRegistry

[seedspirit]

Replace the legacy GlobalActionProcessor wiring of services/idle_checker (create/update/purge/admin_search) with ops-backed actions and ProcessorRegistry factories (global create/search ops), keeping the superadmin gate and API contracts unchanged. Delete services/idle_checker/service.py in favor of the generic services, and update adapter call sites from wait_for_complete to run. Reference migration: services/app_config_allow_list (commit 539ef85). Out of scope: the 7 reconciler-only repository methods stay on repository.py.

Success Criteria

• checker CRUD runs through ProcessorRegistry processors with unchanged REST/GQL contracts
• services/idle_checker/service.py removed; generic services execute the specs
• reconciler paths (judgment/sweep/assignment sync) untouched and passing
• pants test passes for affected packages

JIRA Issue: BA-7276