fix: 用 Zustand 缓存 Feed 列表，返回时恢复滚动且不重复请求

点击 Logo 仍强制刷新；后退忽略 history 上的 refreshFeed，并支持过期静默刷新与下拉刷新。

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

frontend/package-lock.json

@@ -51,7 +51,8 @@
         "tailwindcss": "^3.4.19",
         "tailwindcss-animate": "^1.0.7",
         "turndown": "^7.2.4",
-        "zod": "^4.4.3"
+        "zod": "^4.4.3",
+        "zustand": "^4.5.7"
       },
       "devDependencies": {
         "@types/node": "^25.9.3",
@@ -4480,6 +4481,34 @@
       "funding": {
         "url": "https://github.com/sponsors/colinhacks"
       }
+    },
+    "node_modules/zustand": {
+      "version": "4.5.7",
+      "resolved": "https://registry.npmjs.org/zustand/-/zustand-4.5.7.tgz",
+      "integrity": "sha512-CHOUy7mu3lbD6o6LJLfllpjkzhHXSBlX8B9+qPddUsIfeF5S/UZ5q0kmCsnRqT1UHFQZchNFDDzMbQsuesHWlw==",
+      "license": "MIT",
+      "dependencies": {
+        "use-sync-external-store": "^1.2.2"
+      },
+      "engines": {
+        "node": ">=12.7.0"
+      },
+      "peerDependencies": {
+        "@types/react": ">=16.8",
+        "immer": ">=9.0.6",
+        "react": ">=16.8"
+      },
+      "peerDependenciesMeta": {
+        "@types/react": {
+          "optional": true
+        },
+        "immer": {
+          "optional": true
+        },
+        "react": {
+          "optional": true
+        }
+      }
     }
   }
 }