feat(driver-pwa): top-up fetches commission rate from backend (no hardcoded rate)

Co-Authored-By: claude-flow <ruv@ruv.net>

driver-pwa/frontend/src/pages/TopupPage.tsx

@@ -1,14 +1,14 @@
 import { useState } from "react";
 import { useLocation, useNavigate } from "react-router-dom";
+import { useQuery } from "@tanstack/react-query";
 import { Delete } from "lucide-react";
 import { toast } from "sonner";
-import { topup } from "@/api/driver";
+import { topup, getCommission } from "@/api/driver";
 import { keypadReduce, withCommission } from "@/lib/amount";
 import { formatMoney } from "@/lib/format";
 import { Segment } from "@/components/Segment";
 import { Spinner } from "@/components/Spinner";
 
-const RATE = 0.052;
 const QUICK = ["500", "1000", "2000"];
 const KEYS = ["1", "2", "3", "4", "5", "6", "7", "8", "9", "·", "0", "back"];
 
@@ -19,9 +19,11 @@ export function TopupPage() {
   const [raw, setRaw] = useState("");
   const [method, setMethod] = useState("qr");
   const [busy, setBusy] = useState(false);
+  const { data: commission } = useQuery({ queryKey: ["commission"], queryFn: getCommission });
+  const rate = commission?.rate ?? 0.052; // fallback only while loading
 
   const base = raw ? parseInt(raw, 10) : 0;
-  const { commission, total } = withCommission(base, RATE);
+  const { commission: fee, total } = withCommission(base, rate);
 
   function press(k: string) {
     if (k === "·") return;
@@ -46,7 +48,7 @@ export function TopupPage() {
       <button className="text-muted text-xs mb-3" onClick={() => nav(-1)}>‹ {bucket}</button>
       <p data-testid="amount" className="text-3xl font-extrabold text-center mt-2">{formatMoney(base)}</p>
       <p data-testid="total" className="text-muted text-xs text-center mb-3">
-        к оплате {formatMoney(total)} (комиссия {formatMoney(commission)})
+        к оплате {formatMoney(total)} (комиссия {formatMoney(fee)})
       </p>
 
       <div className="flex gap-1.5 mb-3">