feat(pos): wire POS v2 to live data (board, orders, payments)

POS v2 is now a real, working point of sale at /[locale]/pos2 (was a static
mock). It reuses the existing data layer so it shares the React Query cache and
offline pipeline with the classic POS:

- Table board ← fetchCafeTableBoard (Free/Busy/Reserved/Cleaning, live totals,
  guest-QR badge); polls every 15s. Open a free table to start an order; open a
  busy table to hydrate its existing order (GET order → cart hydrateFromOrder).
- Order screen ← real branch/café menu + categories, bound to useCartStore
  (add/qty/remove). Send via submitOrderToApi (online + offline outbox) then
  re-hydrate; "ارسال (n)" shows the pending (unsynced) line count.
- Pay sheet ← POST /orders/{id}/payments. Cash (numpad + change), Card, and a
  Split helper (records the full amount; split is cashier guidance for now).
- Online/offline badge, loading/empty states, toasts, busy overlay, and a
  "نسخه کلاسیک" link back to /pos.

The static design mock stays at /[locale]/pos2-preview (dev-only, 404 in prod).
tsc --noEmit clean.

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

web/dashboard/src/lib/pos2/use-pos2.ts

@@ -0,0 +1,58 @@
+"use client";
+
+// ─────────────────────────────────────────────────────────────────────────────
+// POS v2 data hooks — thin wrappers over the EXISTING data layer so the new POS
+// UI reuses the same endpoints/query keys as the classic POS (cache-shared).
+// ─────────────────────────────────────────────────────────────────────────────
+
+import { useMemo } from "react";
+import { useQuery } from "@tanstack/react-query";
+import { apiGet } from "@/lib/api/client";
+import { getBranchMenu, branchMenuItemToMenuItem } from "@/lib/api/branch-menu";
+import { fetchCafeTableBoard } from "@/lib/api/branch-tables";
+import type { MenuCategory, MenuItem, TableBoardItem } from "@/lib/api/types";
+
+export function usePos2Categories(cafeId?: string | null) {
+  return useQuery({
+    queryKey: ["menu-categories", cafeId],
+    queryFn: () => apiGet<MenuCategory[]>(`/api/cafes/${cafeId}/menu/categories`),
+    enabled: !!cafeId,
+    staleTime: 60_000,
+  });
+}
+
+/** Branch-scoped menu (effective prices) when a branch is selected; otherwise the
+ *  café-wide menu. Both normalize to MenuItem so the cart store can consume them. */
+export function usePos2Menu(cafeId?: string | null, branchId?: string | null) {
+  return useQuery({
+    queryKey: ["pos2-menu", cafeId, branchId ?? "cafe"],
+    queryFn: async (): Promise<MenuItem[]> => {
+      if (branchId) {
+        const rows = await getBranchMenu(cafeId as string, branchId);
+        return rows.map(branchMenuItemToMenuItem);
+      }
+      return apiGet<MenuItem[]>(`/api/cafes/${cafeId}/menu/items`);
+    },
+    enabled: !!cafeId,
+    staleTime: 30_000,
+  });
+}
+
+export function usePos2Tables(cafeId?: string | null, branchId?: string | null) {
+  return useQuery({
+    queryKey: ["tables-board", cafeId, branchId, "pos"],
+    queryFn: () => fetchCafeTableBoard(cafeId as string, branchId ?? undefined),
+    enabled: !!cafeId,
+    refetchInterval: 15_000,
+  });
+}
+
+export function useMenuById(items: MenuItem[] | undefined): Map<string, MenuItem> {
+  return useMemo(() => {
+    const m = new Map<string, MenuItem>();
+    for (const it of items ?? []) m.set(it.id, it);
+    return m;
+  }, [items]);
+}
+
+export type { MenuCategory, MenuItem, TableBoardItem };