Add PWA install badge for desktop and tablet (manifest, SW, Add to Home Screen).

Co-authored-by: Cursor <cursoragent@cursor.com>

frontend/src/App.tsx

@@ -1,6 +1,7 @@
 import type { ReactNode } from "react";
 import { NavLink, Navigate, Route, Routes } from "react-router-dom";
 import { clearSession, getToken, getUsername } from "./api/client";
+import InstallBadge from "./components/InstallBadge";
 import LoginPage from "./pages/Login";
 import PlanPage from "./pages/Plan";
 import TradesPage from "./pages/Trades";
@@ -14,6 +15,7 @@ function Shell({ children }: { children: ReactNode }) {
       <header className="topnav">
         <div className="topnav-side left">
           <div className="brand">OKX 自动化对冲系统</div>
+          <InstallBadge />
         </div>
         <nav className="topnav-center">
           <NavLink to="/plan" className={({ isActive }) => (isActive ? "active" : "")}>