feat: portal redesign, pricing catalog, partner-staff invites

- portal: new admin/ and partner/ surfaces with full component library
  (AppLauncher, Avatar, Badge, Card, Modal, Tabs, etc.), composables,
  layouts, partner-routing middleware, and supporting server APIs
- pricing: Price schema/module with operator CRUD, pricing.vue catalog UI,
  Subscription extended with cycle/currency/perSeatAmount/seats snapshots
  for stable MRR aggregation
- partner staff: User.partnerId, invite-partner-user DTO and flow,
  /partners/:slug/users endpoints, InvitePartnerUserModal, shared
  dezky-partner-staff Authentik group
- /me: partner-aware endpoint returning user + partner context so portal
  can route between end-user and partner-admin surfaces
- tenant: seats field for portfolio displays and future MRR calculations
- operator: pricing page, signed-out page, useMe/useToast composables,
  ToastStack

services/platform-api/src/schemas/tenant.schema.ts

@@ -25,6 +25,14 @@ export class Tenant {
   @Prop({ enum: ['mvp', 'pro', 'enterprise'], default: 'mvp' })
   plan!: TenantPlan
 
+  // Initial seat count from provisioning. Used for portfolio displays and
+  // (later) MRR calculations. The "used" count comes from User.tenantIds —
+  // not stored here to avoid a denormalized field that drifts on every
+  // user-add/remove. Default 0 so older docs without this field render
+  // as "0 / N" without throwing.
+  @Prop({ type: Number, min: 0, default: 0 })
+  seats!: number
+
   // Custom domains attached to this tenant. First entry is the primary host.
   @Prop({ type: [String], default: [] })
   domains!: string[]