refactor(portal): partner-mode customer switcher on real tenants

Migrate the partner-mode customer switcher, in-customer banner, sidebar tile and the team invite/teammate panels off the data/customers fixture onto the real /api/partner/tenants list (shared key, gated to partner-staff so the global shell doesn't 403 for other users). Active customer resolves by tenant _id (the key the customers page already passes to partnerMode.enter); partner-identity labels now use the real partner name from useMe. Removes the now-unused customers + CustomerOrg-list fixture export and the dead setCustomer helper. Verified in UI: switcher + enter/exit show real Baslund Test / Baslund Research ApS.

apps/portal/composables/usePartnerMode.ts

@@ -4,9 +4,8 @@
 //
 // In real use, every action while in this mode is logged with the partner's
 // identity (not the customer's) — the design spec is explicit about this for
-// trust. For the prototype we just hold the customer id.
-
-import type { CustomerOrg } from '~/types/partner'
+// trust. We hold the active customer's tenant _id (the same key the customers
+// page passes to enter()); consumers resolve it against the real tenant list.
 
 const activeCustomerId = ref<string | null>(null)
 
@@ -34,8 +33,5 @@ export const usePartnerMode = () => {
     enter,
     exit,
     hydrate,
-    setCustomer: (c: CustomerOrg | null) => {
-      activeCustomerId.value = c?.id ?? null
-    },
   }
 }