fix: v1.4 Bug 修复与体验优化

- 修复所有日期相关逻辑使用 UTC 导致时区偏移问题
- 首页今日数据改用 stats API 聚合查询，消除 100 条上限
- 账单分页加载添加请求序号，防止并发覆盖
- 统计页 maxSingle 改为按金额排序
- 统计页 tab 切换时刷新月对比数据
- 首页 onShow 跳过首次加载，避免双重请求
- 今日卡片同时展示支出/收入，骨架屏对齐
- 账单页统一左滑删除，去掉长按
- 后端 transaction 支持 sortBy 参数
- 后端 stats overview 支持 startDate/endDate 查询

client/src/pages/add/index.vue

@@ -67,12 +67,14 @@ const type = ref<'expense' | 'income'>('expense')
 const amountStr = ref('0')
 const selectedCat = ref<number | null>(null)
 const note = ref('')
-const selectedDate = ref(new Date().toISOString().slice(0, 10))
+const now = new Date()
+const localToday = `${now.getFullYear()}-${String(now.getMonth() + 1).padStart(2, '0')}-${String(now.getDate()).padStart(2, '0')}`
+const selectedDate = ref(localToday)
 const saving = ref(false)
 const editId = ref<number | null>(null)
 const showSuccess = ref(false)
 const scrollToCat = ref('')
-const todayStr = new Date().toISOString().slice(0, 10)
+const todayStr = localToday
 // Remember last selected category per type
 const lastCatByType: Record<string, number | null> = { expense: null, income: null }