feat(adminfinance): 新增预计收入指标并优化明细查询性能

- 财务看板增加预计收入与待结算订单数统计
- 明细列表 COUNT 改为仅扫描 rental_orders 主表，避免 5-JOIN 子查询
- 统一前后端结算差异判定阈值为常量 5 分
- 修复日期选择器使用 UTC 日期导致东八区凌晨偏移前一天的问题

backend/internal/modules/adminfinance/detail.go

@@ -7,14 +7,20 @@ import (
 )
 
 func (r *Repository) Details(ctx context.Context, query DetailQuery) (*PaginatedResult, error) {
-	baseDB := r.db.WithContext(ctx)
-	db := r.financeDetailBaseQuery(ctx, query)
+	// COUNT 只扫描 rental_orders 主表(过滤条件全部落在 ro.* 上,可命中
+	// idx_rental_orders_settled_at_id / created_at_id 索引),不再套完整 5-JOIN
+	// 子查询,避免大数据量翻页时 COUNT 拖慢。
+	countDB := r.applyDetailFilters(r.db.WithContext(ctx).Table("rental_orders AS ro"), query)
 	var total int64
-	countDB := baseDB.Table("(?) AS finance_rows", db)
 	if err := countDB.Count(&total).Error; err != nil {
 		return nil, err
 	}
+	if total == 0 {
+		return &PaginatedResult{Items: []FinanceDetailDTO{}, Total: 0, Page: query.Page, PageSize: query.PageSize}, nil
+	}
 
+	// 明细行查询保留完整 JOIN,仅对当前分页命中的订单做金额聚合。
+	db := r.financeDetailBaseQuery(ctx, query)
 	offset := (query.Page - 1) * query.PageSize
 	rows := make([]financeDetailRow, 0, query.PageSize)
 	if err := db.Order("ro.id DESC").Offset(offset).Limit(query.PageSize).Scan(&rows).Error; err != nil {
@@ -27,6 +33,31 @@ func (r *Repository) Details(ctx context.Context, query DetailQuery) (*Paginated
 	return &PaginatedResult{Items: items, Total: total, Page: query.Page, PageSize: query.PageSize}, nil
 }
 
+// applyDetailFilters 把仅依赖 rental_orders 主表字段的过滤条件挂到查询上,
+// COUNT 与明细行查询共用,保证两者口径一致。
+func (r *Repository) applyDetailFilters(db *gorm.DB, query DetailQuery) *gorm.DB {
+	if query.OrderNo != "" {
+		db = db.Where("ro.order_no = ?", query.OrderNo)
+	}
+	if query.UserID > 0 {
+		db = db.Where("(ro.renter_id = ? OR ro.owner_id = ?)", query.UserID, query.UserID)
+	}
+	if query.OrderStatus != "" {
+		db = db.Where("ro.status = ?", query.OrderStatus)
+	}
+	if query.SettlementStatus != "" {
+		db = db.Where("ro.settlement_status = ?", query.SettlementStatus)
+	}
+	if !query.StartDate.IsZero() && !query.EndDate.IsZero() {
+		if query.DateType == "created" {
+			db = db.Where("ro.created_at >= ? AND ro.created_at <= ?", query.StartDate, query.EndDate)
+		} else {
+			db = db.Where("ro.settled_at >= ? AND ro.settled_at <= ?", query.StartDate, query.EndDate)
+		}
+	}
+	return db
+}
+
 func (r *Repository) financeDetailBaseQuery(ctx context.Context, query DetailQuery) *gorm.DB {
 	db := r.db.WithContext(ctx).Table("rental_orders AS ro").
 		Select(`ro.id AS order_id, ro.order_no, ro.status AS order_status, ro.settlement_status, ro.refund_status,
@@ -48,34 +79,15 @@ func (r *Repository) financeDetailBaseQuery(ctx context.Context, query DetailQue
 				CASE
 					WHEN COALESCE(p.failed_refund_amount_cent, 0) > 0 THEN 'refund_failed'
 					WHEN COALESCE(p.refunding_amount_cent, 0) > 0 OR ro.refund_status = 'refunding' THEN 'refund_pending'
-					WHEN ABS(COALESCE(oc.owner_income_amount_cent, 0) - COALESCE(w.owner_wallet_income_amount_cent, 0)) >= 5 THEN 'settlement_diff'
+					WHEN ABS(COALESCE(oc.owner_income_amount_cent, 0) - COALESCE(w.owner_wallet_income_amount_cent, 0)) >= ? THEN 'settlement_diff'
 				ELSE 'normal'
 			END AS finance_status,
-			ro.created_at, ro.settled_at`).
+			ro.created_at, ro.settled_at`, settlementDiffThresholdCent).
 		Joins("LEFT JOIN users AS ru ON ru.id = ro.renter_id").
 		Joins("LEFT JOIN users AS ou ON ou.id = ro.owner_id").
 		Joins("LEFT JOIN (?) AS oc ON oc.order_id = ro.id", acceptedCheckoutSubquery(r.db.WithContext(ctx))).
 		Joins("LEFT JOIN (?) AS p ON p.order_id = ro.id", orderPaymentSubquery(r.db.WithContext(ctx))).
 		Joins("LEFT JOIN (?) AS w ON w.order_id = ro.id", ownerWalletIncomeSubquery(r.db.WithContext(ctx)))
 
-	if query.OrderNo != "" {
-		db = db.Where("ro.order_no = ?", query.OrderNo)
-	}
-	if query.UserID > 0 {
-		db = db.Where("(ro.renter_id = ? OR ro.owner_id = ?)", query.UserID, query.UserID)
-	}
-	if query.OrderStatus != "" {
-		db = db.Where("ro.status = ?", query.OrderStatus)
-	}
-	if query.SettlementStatus != "" {
-		db = db.Where("ro.settlement_status = ?", query.SettlementStatus)
-	}
-	if !query.StartDate.IsZero() && !query.EndDate.IsZero() {
-		if query.DateType == "created" {
-			db = db.Where("ro.created_at >= ? AND ro.created_at <= ?", query.StartDate, query.EndDate)
-		} else {
-			db = db.Where("ro.settled_at >= ? AND ro.settled_at <= ?", query.StartDate, query.EndDate)
-		}
-	}
-	return db
+	return r.applyDetailFilters(db, query)
 }