fix(dashboard): review fixes — error toasts, dedupe socket, POS guards

- Global MutationCache.onError safety net so mutations without their own onError
  no longer fail silently (skips ones that handle errors → no double toast).
- Notifications feed no longer opens its own SignalR connection; it reuses the
  one in useOrderAlerts (was double sockets + double cache churn per session).
- "Send test notification" now works on the settings page (force flag bypasses
  the tab-visible guard) instead of silently doing nothing.
- POS: re-entry guard on payment confirm (no duplicate payment on double-tap);
  notes on already-sent lines are read-only (a note-only edit was silently lost);
  ORDER_ALREADY_CLOSED surfaced with a clear Persian message.
- Reservation Confirm/Cancel/Complete buttons disabled while pending.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

web/dashboard/src/components/pos2/pos2-screen.tsx

@@ -7,7 +7,7 @@
 // Mounted at /[locale]/pos (and /pos2). Design mirrors pos2-prototype.tsx.
 // ─────────────────────────────────────────────────────────────────────────────
 
-import { useEffect, useMemo, useState } from "react";
+import { useEffect, useMemo, useRef, useState } from "react";
 import { useMutation, useQuery, useQueryClient } from "@tanstack/react-query";
 import {
   Search, Plus, Minus, Trash2, Send, CreditCard, SplitSquareHorizontal,
@@ -123,6 +123,7 @@ export function Pos2Screen() {
   const [payLoyalty, setPayLoyalty] = useState(0);
   // Order just paid — kept after the cart is cleared so the receipt stays printable.
   const [paidOrderId, setPaidOrderId] = useState<string | null>(null);
+  const payingRef = useRef(false); // re-entry guard for the payment confirm
 
   const [online, setOnline] = useState(true);
   useEffect(() => {
@@ -275,7 +276,8 @@ export function Pos2Screen() {
   };
 
   const confirmPay = async (payments: Payment[], loyaltyRedeem: number) => {
-    if (!payTarget) return;
+    if (!payTarget || payingRef.current) return; // guard against a double-tap
+    payingRef.current = true;
     setBusy(true);
     try {
       const cardTotal = payments.filter((p) => p.method === "Card").reduce((s, p) => s + p.amount, 0);
@@ -306,10 +308,13 @@ export function Pos2Screen() {
         notify.error(posDeviceMsg(e));
       } else if (e instanceof ApiClientError && e.code === "NO_OPEN_SHIFT") {
         notify.error("برای پرداخت باید شیفت باز باشد");
+      } else if (e instanceof ApiClientError && e.code === "ORDER_ALREADY_CLOSED") {
+        notify.error("این سفارش قبلاً تسویه شده است");
       } else {
         notify.error(errMsg(e, "ثبت پرداخت ناموفق بود"));
       }
     } finally {
+      payingRef.current = false;
       setBusy(false);
     }
   };
@@ -355,7 +360,11 @@ export function Pos2Screen() {
   );
 
   const ticketProps = {
-    cafeId, lines: live, subtotal, discount, tax, total, count, pendingCount,
+    cafeId,
+    // mark fully-sent lines so their note becomes read-only (a note-only change on
+    // an already-sent line would otherwise be silently dropped on the next send).
+    lines: live.map((l) => ({ ...l, synced: (syncedQty[l.menuItem.id] ?? 0) >= l.quantity })),
+    subtotal, discount, tax, total, count, pendingCount,
     onBump: (id: string, d: number) => { const l = items.find((x) => x.menuItem.id === id); if (l) updateQty(id, l.quantity + d); },
     onRemove: removeItem, onSend: send, onPay: openPay, onSplit: openPay,
     onNote: (id: string, notes: string) => setNotes(id, notes),
@@ -732,7 +741,7 @@ function Pos2Extras({ cafeId }: { cafeId: string }) {
 }
 
 // ── Order ticket ─────────────────────────────────────────────────────────────
-type TicketLine = { menuItem: MenuItem; quantity: number; notes?: string };
+type TicketLine = { menuItem: MenuItem; quantity: number; notes?: string; synced?: boolean };
 function Ticket({
   cafeId, lines, subtotal, discount, tax, total, count, pendingCount, onBump, onRemove, onNote, onSend, onPay, onSplit, canPrint, onPrintReceipt,
 }: {
@@ -775,7 +784,14 @@ function Ticket({
                     <Trash2 className="size-4" />
                   </button>
                 </div>
-                {noteFor === l.menuItem.id || l.notes ? (
+                {l.synced ? (
+                  // Already sent to the kitchen — note is read-only (can't be changed now).
+                  l.notes ? (
+                    <p className="mt-1.5 flex items-center gap-1.5 text-xs text-muted-foreground">
+                      <StickyNote className="size-3.5 shrink-0" /> {l.notes}
+                    </p>
+                  ) : null
+                ) : noteFor === l.menuItem.id || l.notes ? (
                   <input
                     value={l.notes ?? ""}
                     onChange={(e) => onNote(l.menuItem.id, e.target.value)}