RBAC role tiers

Five ordered access levels — free account, the ทั้งคลัง package, the ทั้งระบบ package, GB (case-study partners), and admin — gate the platform from read-only articles up through the full calculator library, the flagship apps, the Case Study section, and admin tools.

• You're deciding what a new feature should be gated behind
• You're debugging why a user can't see a calculator or the Case Study section
• You need to explain the access model to a customer asking what their plan unlocks

A free account reads articles and uses EVERY calculator in full — deep features included; the ทั้งระบบ package adds the flagship apps (Model Builder, PHA/HAC, commissioning); GB adds the Case Study section; admin adds site administration. Gating is enforced with hooks like useIsPro() / useIsGB() and the SubscriberGate component, backed by a server-side role check.