fix: 修复列表页浮动添加按钮被底部Tabbar遮挡的问题

将列表页浮动添加按钮的bottom值从24px调整为80px：
- receivable/List.vue
- expense/List.vue
- requirement/List.vue

Tabbar高度64px，添加按钮需要预留足够空间避免被遮挡

fund-mobile/src/views/expense/List.vue

@@ -201,7 +201,7 @@ const handleSearch = () => {
 
 .add-btn {
   position: fixed;
-  bottom: 24px;
+  bottom: 80px;
   right: 24px;
   width: 56px;
   height: 56px;

fund-mobile/src/views/receivable/List.vue

@@ -261,7 +261,7 @@ onMounted(() => {
 
 .add-btn {
   position: fixed;
-  bottom: 24px;
+  bottom: 80px;
   right: 24px;
   width: 56px;
   height: 56px;

fund-mobile/src/views/requirement/List.vue

@@ -217,7 +217,7 @@ const handleSearch = () => {
 
 .add-btn {
   position: fixed;
-  bottom: 24px;
+  bottom: 80px;
   right: 24px;
   width: 56px;
   height: 56px;