重构预算管理模块，添加预算记录和服务，更新相关API，优化预算统计逻辑

Web/src/App.vue

@@ -9,9 +9,6 @@
         <van-tabbar-item name="statistics" icon="chart-trending-o" to="/" @click="handleTabClick('/statistics')">
           统计
         </van-tabbar-item>
-        <van-tabbar-item name="budget" icon="bill-o" to="/budget" @click="handleTabClick('/budget')">
-          预算
-        </van-tabbar-item>
         <van-tabbar-item 
           name="balance" 
           icon="balance-list" 
@@ -21,6 +18,9 @@
         >
           账单
         </van-tabbar-item>
+        <van-tabbar-item name="budget" icon="bill-o" to="/budget" @click="handleTabClick('/budget')">
+          预算
+        </van-tabbar-item>
         <van-tabbar-item name="setting" icon="setting" to="/setting">
           设置
         </van-tabbar-item>