feat(appointment): log cancellation events and show them in a Timeline

Introduce the first per-appointment event system. On cancel (via the status
or general update endpoints) an AppointmentEvent (type=cancelled, «نوبت لغو
شد») is recorded with the actor, cancel time, and an optional cancel_reason,
plus a warning-level app_log entry. New GET /appointment/{uuid}/events
returns the ordered event list. The admin appointment detail page renders a
Timeline section and the cancel dialog now collects an optional reason.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

assets/admin/components/ui/ConfirmDialog.tsx

@@ -12,6 +12,8 @@ interface Props {
   loading?: boolean;
   onConfirm: () => void;
   onCancel: () => void;
+  /** محتوای اضافه زیر پیام (مثلاً فیلد دلیل). */
+  children?: React.ReactNode;
 }
 
 export default function ConfirmDialog({
@@ -24,6 +26,7 @@ export default function ConfirmDialog({
   loading = false,
   onConfirm,
   onCancel,
+  children,
 }: Props) {
   if (!open) return null;
 
@@ -48,6 +51,7 @@ export default function ConfirmDialog({
         </div>
         <div className="modal-body">
           <p style={{ color: 'var(--text-2)', lineHeight: 1.75, margin: 0 }}>{message}</p>
+          {children}
         </div>
         <div className="modal-foot" style={{ justifyContent: 'flex-end' }}>
           <button className="btn ghost sm" onClick={onCancel} disabled={loading}>