feat(membership): enforce tenant subscription plans with blocked UI

Add configurable membership plans (free/plus/pro) synced to DB on boot, a
subscription guard middleware that blocks tenant endpoints on expired or
missing plans, and a MembershipBlockedView that surfaces the reason so
the admin can contact the tenant owner. Quota and brand-library reads now
honor the active plan's policy JSON and expired subscriptions.

packages/shared-types/src/index.ts

@@ -30,9 +30,25 @@ export interface UserInfo {
   tenant_id: number;
   tenant_role: string;
   permissions: string[];
+  membership: MembershipInfo | null;
   kol_profile: KolProfileBrief | null;
 }
 
+export interface MembershipInfo {
+  plan_code: string;
+  plan_name: string;
+  status: string;
+  blocked: boolean;
+  blocked_reason: string | null;
+  start_at: string | null;
+  end_at: string | null;
+  article_generation_limit: number;
+  article_quota_cycle: string;
+  company_limit: number;
+  image_storage_bytes: number;
+  contact_admin_on_expiry: boolean;
+}
+
 export interface LoginResponse {
   access_token: string;
   refresh_token: string;