Staff can now click "View as Customer" on any client profile in the admin
panel. This navigates to the customer portal with impersonation auto-activated,
showing the portal exactly as that customer would see it (read-only, with
full audit trail).
The portal reads impersonate/clientName/reason/staffName from URL search
params on mount, auto-starts the impersonation session, then cleans up the
URL.
Co-Authored-By: Paperclip <noreply@paperclip.ing>