fix(web): 项目主图标统一替换为昔涟3rd_Form-Cyrene-3F-Q-Happy-1.png

- favicon/apple-touch-icon (index.html)
- PWA manifest 图标 (manifest.json)
- PWA precache (sw.js)
- 用户端侧栏品牌头像 (Nav.tsx)
- 管理面板顶栏品牌头像 (AdminApp.tsx)
- 删除已被替换的 icon.svg 残留引用

frontend/web/public/manifest.json

@@ -9,10 +9,10 @@
   "orientation": "any",
   "icons": [
     {
-      "src": "/icon.svg",
-      "type": "image/svg+xml",
-      "sizes": "any",
-      "purpose": "any maskable"
+      "src": "/images/Cyrene_Avatar/3rd_Form/Cyrene-3F-Q-Happy-1.png",
+      "type": "image/png",
+      "sizes": "1500x1500",
+      "purpose": "any"
     }
   ]
 }