chore(spec): 归档 blog-5n——八任务收敛（后台深度优化全家桶）

Spec: 2026-11-05_blog-5n-admin-deep-optimization

Co-authored-by: GLM-5.3

public/admin/manifest.webmanifest

@@ -0,0 +1,21 @@
+{
+  "name": "wait4x 后台",
+  "short_name": "后台",
+  "start_url": "/admin/",
+  "scope": "/admin/",
+  "display": "standalone",
+  "background_color": "#ffffff",
+  "theme_color": "#3454d1",
+  "icons": [
+    {
+      "src": "/icons/icon-192.png",
+      "sizes": "192x192",
+      "type": "image/png"
+    },
+    {
+      "src": "/icons/icon-512.png",
+      "sizes": "512x512",
+      "type": "image/png"
+    }
+  ]
+}