fix(portal): add onClick handler to Reschedule button

Reschedule buttons in Dashboard and Appointments had no onClick handler,
making them no-ops. Add type="button" to prevent accidental form submission
and an alert() placeholder until the reschedule modal is implemented.

Fixes GRO-166.

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
+                type="button"
+                className="text-xs px-3 py-1.5 border border-stone-200 rounded-lg text-stone-600 hover:bg-stone-50"
+                onClick={() => alert("Rescheduling is coming soon!")}
+              >
                 Reschedule
               </button>
               <CancelAppointmentButton appointment={appt} sessionId={sessionId} />

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

@@ -77,7 +77,11 @@ export function Dashboard({ onNavigate, readOnly }: Props) {
           </div>
           {!readOnly && (
             <div className="flex gap-2 mt-4">
-              <button className="text-sm px-3 py-1.5 border border-stone-200 rounded-lg text-stone-600 hover:bg-stone-50">
+              <button
+                type="button"
+                className="text-sm px-3 py-1.5 border border-stone-200 rounded-lg text-stone-600 hover:bg-stone-50"
+                onClick={() => alert("Rescheduling is coming soon!")}
+              >
                 Reschedule
               </button>
               <button className="text-sm px-3 py-1.5 border border-stone-200 rounded-lg text-stone-600 hover:bg-stone-50">