Support Meta's Marketing Messages API (/marketing_messages) for WhatsApp numbers

Meta routes MARKETING templates to /marketing_messages (MM API for WhatsApp) with delivery optimisation, and max-price bidding enters open beta on 1 Oct 2026 (required in eligible markets from Q2 2027, when fixed marketing rates will only apply on Cloud API). Our Meta-direct numbers already send marketing templates through it; our Zernio coexistence numbers cannot. Please add an option (e.g. on POST /v1/whatsapp/templates/send or broadcasts) to send MARKETING templates via the MM API, and pass pricing.category = marketing_lite back on status webhooks.