feat(billing): rating engine, fechamento de periodo, dashboard platform (fase 22)

Fecha a orquestracao de Billing (agente.md secao 120-139) sobre o schema/
RatingEngine puro ja existentes: escritores do ledger UsageEvent
(CALL_SECONDS no CDR, ACTIVE_DAY via sweep diario), closeBillingPeriod/
reopenBillingPeriod (fechamento imutavel com audit trail), e os
controllers de price books/rate decks/plan versions/subscriptions/
periods/statements. Corrige 2 bugs reais de RLS achados no teste ponta a
ponta (reopen sem tenant context, subscriptions sem withTenantContext) e
adiciona teste unitario do RatingEngine (17 casos).

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01EWHKmcVJtstQFErbZ1AanY

apps/api/package.json

@@ -11,6 +11,7 @@
   "dependencies": {
     "@b2bcall/ai": "workspace:*",
     "@b2bcall/auth": "workspace:*",
+    "@b2bcall/billing": "workspace:*",
     "@b2bcall/database": "workspace:*",
     "@b2bcall/entitlements": "workspace:*",
     "@b2bcall/shared": "workspace:*",