KnowledgeVault AI module-spec M-10

M-10 delivers an admin-only analytics panel that surfaces aggregate platform impact (hours of expert knowledge preserved, support-call reduction estimate) and AI cost efficiency metrics (cost per session, cost per knowledge chunk, total AI spend). A pre-aggregated PostgreSQL materialized view — platform_analytics_mv — ensures sub-2-second API response time regardless of dataset size. Access is enforced via Supabase Auth admin-role check on every request; unauthenticated callers receive 401 and n