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

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

frontend/public/manifest.webmanifest

@@ -0,0 +1,34 @@
+{
+  "name": "OKX 自动化对冲系统",
+  "short_name": "对冲系统",
+  "description": "ETH 永续+期权对冲监控与策略控制台",
+  "start_url": "/plan",
+  "scope": "/",
+  "display": "standalone",
+  "display_override": ["standalone", "minimal-ui", "browser"],
+  "orientation": "any",
+  "background_color": "#0b0e11",
+  "theme_color": "#0b0e11",
+  "lang": "zh-CN",
+  "categories": ["finance", "productivity"],
+  "icons": [
+    {
+      "src": "/icons/icon-192.png",
+      "sizes": "192x192",
+      "type": "image/png",
+      "purpose": "any"
+    },
+    {
+      "src": "/icons/icon-512.png",
+      "sizes": "512x512",
+      "type": "image/png",
+      "purpose": "any"
+    },
+    {
+      "src": "/icons/icon-512.png",
+      "sizes": "512x512",
+      "type": "image/png",
+      "purpose": "maskable"
+    }
+  ]
+}