feat: 用户体验优化 — 首页加载/继续记账/登录恢复

## 首页加载优化
- 分级加载：首屏只请求 overview + recentTx（2个请求）
- 数据新鲜度：30秒内不重复请求
- 次要数据异步加载：budget + todayData
- 非关键数据后台加载：userInfo + notifications

## 继续记账功能
- SaveSuccess 组件新增「继续记一笔」按钮
- 新增模式显示继续按钮，编辑模式自动返回
- 继续记账时保留分类和日期，清空金额和备注

## 登录失败恢复
- 登录重试机制：最多3次，间隔1秒
- 失败后显示提示而非静默等待

## 群组账单逻辑修正
- 群组账单 = 所有群组成员的个人账单之和
- 修改查询：WHERE user_id IN (群组成员)

client/src/components/SaveSuccess/SaveSuccess.vue

@@ -1,9 +1,19 @@
 <template>
-  <view class="save-success" v-if="visible" @tap="hide">
-    <view class="success-icon" :class="{ show: animating }">
-      <Icon name="check" :size="80" color="#FFFFFF" />
+  <view class="save-success" v-if="visible">
+    <view class="success-content" :class="{ show: animating }">
+      <view class="success-icon">
+        <Icon name="check" :size="80" color="#FFFFFF" />
+      </view>
+      <text class="success-text">{{ text }}</text>
+      <view class="success-actions" v-if="showContinue">
+        <view class="action-btn continue" @tap="onContinue">
+          <text class="action-text">继续记一笔</text>
+        </view>
+        <view class="action-btn back" @tap="onBack">
+          <text class="action-text">返回</text>
+        </view>
+      </view>
     </view>
-    <text class="success-text" :class="{ show: animating }">{{ text }}</text>
   </view>
 </template>
 
@@ -14,51 +24,61 @@ import Icon from '@/components/Icon/Icon.vue'
 const props = withDefaults(defineProps<{
   visible: boolean
   text?: string
-}>(), { text: '保存成功' })
+  showContinue?: boolean
+}>(), { text: '保存成功', showContinue: false })
 
-const emit = defineEmits(['update:visible'])
+const emit = defineEmits(['update:visible', 'continue', 'back'])
 
 const animating = ref(false)
 
 watch(() => props.visible, (val) => {
   if (val) {
     setTimeout(() => { animating.value = true }, 50)
-    setTimeout(() => { hide() }, 2000)
+    // 如果不显示继续按钮，自动关闭
+    if (!props.showContinue) {
+      setTimeout(() => { onBack() }, 2000)
+    }
   } else {
     animating.value = false
   }
 })
 
-function hide() {
+function onContinue() {
   animating.value = false
-  setTimeout(() => { emit('update:visible', false) }, 300)
+  setTimeout(() => {
+    emit('update:visible', false)
+    emit('continue')
+  }, 300)
+}
+
+function onBack() {
+  animating.value = false
+  setTimeout(() => {
+    emit('update:visible', false)
+    emit('back')
+  }, 300)
 }
 </script>
 
 <style lang="scss" scoped>
+@import '@/styles/mixins.scss';
+
 .save-success {
   position: fixed;
   top: 0;
   left: 0;
   right: 0;
   bottom: 0;
-  display: flex;
-  flex-direction: column;
-  align-items: center;
-  justify-content: center;
+  @include flex-center;
   background: rgba(0, 0, 0, 0.5);
   z-index: 9999;
 }
 
-.success-icon {
-  width: 160rpx;
-  height: 160rpx;
-  border-radius: 50%;
-  background: linear-gradient(135deg, #7BC67E, #5BA85E);
+.success-content {
   display: flex;
+  flex-direction: column;
   align-items: center;
-  justify-content: center;
-  transform: scale(0);
+  transform: scale(0.8);
   opacity: 0;
   transition: all 0.3s cubic-bezier(0.34, 1.56, 0.64, 1);
 
@@ -68,18 +88,47 @@ function hide() {
   }
 }
 
-.success-text {
-  font-size: 32rpx;
-  font-weight: 600;
-  color: #FFFFFF;
-  margin-top: 24rpx;
-  transform: translateY(20rpx);
-  opacity: 0;
-  transition: all 0.3s ease 0.2s;
+.success-icon {
+  width: 160rpx;
+  height: 160rpx;
+  border-radius: 50%;
+  background: linear-gradient(135deg, $success, #5BA85E);
+  @include flex-center;
+}
 
-  &.show {
-    transform: translateY(0);
-    opacity: 1;
+.success-text {
+  font-size: $font-xl;
+  font-weight: 600;
+  color: $surface;
+  margin-top: $space-lg;
+}
+
+.success-actions {
+  display: flex;
+  gap: $space-md;
+  margin-top: $space-2xl;
+}
+
+.action-btn {
+  padding: $space-sm $space-xl;
+  border-radius: $radius-xl;
+  min-width: 200rpx;
+  @include flex-center;
+
+  &.continue {
+    background: $primary;
+    &:active { opacity: 0.8; }
+  }
+
+  &.back {
+    background: rgba(255, 255, 255, 0.2);
+    &:active { background: rgba(255, 255, 255, 0.3); }
   }
 }
+
+.action-text {
+  font-size: $font-lg;
+  font-weight: 600;
+  color: $surface;
+}
 </style>