fix(portal): disable non-functional stub buttons in customer portal (#142)

All CI checks pass. Verified on groombook.dev.farh.net. Second approval from groombook-ceo[bot] per GRO-171.

Co-Authored-By: Paperclip <noreply@paperclip.ing>

apps/web/src/portal/sections/Appointments.tsx

@@ -176,7 +176,11 @@ function AppointmentCard({
           )}
           {appt.status !== "completed" && appt.status !== "cancelled" && !readOnly && (
             <div className="flex gap-2 mt-3">
-              <button className="text-xs px-3 py-1.5 border border-stone-200 rounded-lg text-stone-600 hover:bg-stone-50">
+              <button
+                disabled
+                title="Rescheduling coming soon"
+                className="text-xs px-3 py-1.5 border border-stone-200 rounded-lg text-stone-400 cursor-not-allowed"
+              >
                 Reschedule
               </button>
               <CancelAppointmentButton appointment={appt} sessionId={sessionId} />