test: 后端测试从 SQLite 全面切换到 MySQL，与生产环境对齐

测试库不再使用 SQLite 内存库，改为每个测试包独立的 MySQL 库，
表结构由 backend/migrations 的真实迁移建立。

基础设施
- 新增 internal/database/testdb.go：NewTestDB() 保持原签名（28 处调用零改动），
  内部连接 MySQL 测试库，首次调用重建库并执行全部真实迁移，之后每次调用清空全表
- 库名 = 测试库基础名 + 包目录名，同包共享、跨包隔离，使 go test ./... 可并发执行
  （共用一库时各包会互相 DROP/CREATE 导致 database exists）
- 新增 NewDryRunDB()：MySQL 方言 + DryRun，供断言 SQL 形态的 5 处测试使用
- 新增 AutoMigrateIfMissing()：只对不存在的表 AutoMigrate，
  避免改动迁移定义的索引与约束
- 新增 scripts/prepare-test-db.sh：建库与通配授权，可重复执行
- 33 处 sqlite.Open 全部替换，26 个测试文件改用 MySQL
- 删除 46 处手写 SQLite 方言 DDL（AUTOINCREMENT / INTEGER PRIMARY KEY / TEXT），
  表统一由真实迁移建立
- go.mod 移除 gorm.io/driver/sqlite 与 mattn/go-sqlite3
- 删除生产代码里 distribution/repository.go 的 sqlite 方言分支（strftime）

对齐环境后暴露并修复的真实问题
- DATE(col) 在 MySQL 返回 DATE 类型，使 Date string 字段变成 RFC3339 时间串，
  大盘日期会带出时间部分；28 处改为 DATE_FORMAT(col, '%Y-%m-%d')
- 系统自动创建分销结算批次时 created_by 写入 0，违反指向 admin_users 的外键，
  生产会直接插入失败；改为写 NULL（新增 adminRef helper）
- MySQL DATETIME 仅到秒，静默截断 Go 侧写入的时间，
  导致租用时长计算与结算时点回读比对偏差；
  rental_orders 的 9 个业务时间列提到 DATETIME(6)
- 测试数据补齐严格模式要求的 NOT NULL 列、修正超出列长的取值、补齐外键父记录

迁移
- 000065 的 ALTER TABLE rental_orders 一并完成业务时间列精度调整，
  feature 侧不再单开迁移文件

脚本与文档
- check.sh / check-backend-coverage.sh 去掉 -p 1 串行与 SQLite 相关注释
- 更新 docs/Repository层测试补充总结.md 的测试运行说明

backend/internal/modules/adminfinance/dashboard.go

@@ -240,22 +240,22 @@ func (r *Repository) dailyItems(ctx context.Context, query DashboardQuery) (dash
 
 	pickupProfits := make([]dailyPickupProfitRow, 0)
 	if err := db.Table("admin_pickups").
-		Select(`DATE(completed_at) AS date,
+		Select(`DATE_FORMAT(completed_at, '%Y-%m-%d') AS date,
 			COALESCE(SUM(profit_amount_cent), 0) AS profit_amount_cent,
 			COUNT(id) AS completed_count`).
 		Where("status = ?", "completed").
 		Where("completed_at >= ? AND completed_at <= ?", query.StartDate, query.EndDate).
-		Group("DATE(completed_at)").
+		Group("DATE_FORMAT(completed_at, '%Y-%m-%d')").
 		Scan(&pickupProfits).Error; err != nil {
 		return dashboardDailyResult{}, err
 	}
 	pickupAdjustments := make([]dailyPickupAdjustmentRow, 0)
 	if err := db.Table("admin_pickup_financial_adjustments AS fa").
-		Select(`DATE(fa.created_at) AS date,
+		Select(`DATE_FORMAT(fa.created_at, '%Y-%m-%d') AS date,
 			COALESCE(SUM(fa.profit_delta_cent), 0) AS profit_amount_cent`).
 		Joins("JOIN admin_pickups AS p ON p.id = fa.pickup_id AND p.status = ?", "completed").
 		Where("fa.created_at >= ? AND fa.created_at <= ?", query.StartDate, query.EndDate).
-		Group("DATE(fa.created_at)").
+		Group("DATE_FORMAT(fa.created_at, '%Y-%m-%d')").
 		Scan(&pickupAdjustments).Error; err != nil {
 		return dashboardDailyResult{}, err
 	}
@@ -388,13 +388,13 @@ func (r *Repository) dailyItems(ctx context.Context, query DashboardQuery) (dash
 func (r *Repository) dailyEstimates(ctx context.Context, query DashboardQuery) ([]dailyEstimatedRow, error) {
 	rows := make([]dailyEstimatedRow, 0)
 	err := r.db.WithContext(ctx).Table("rental_orders").
-		Select(`DATE(created_at) AS date,
+		Select(`DATE_FORMAT(created_at, '%Y-%m-%d') AS date,
 			COALESCE(SUM(platform_fee_cent), 0) AS estimated_income_amount_cent,
 			COUNT(id) AS pending_settle_order_count`).
 		Where("settlement_status NOT IN ?", settledSettlementStatuses()).
 		Where("status NOT IN ?", nonBillableOrderStatuses()).
 		Where("created_at >= ? AND created_at <= ?", query.StartDate, query.EndDate).
-		Group("DATE(created_at)").
+		Group("DATE_FORMAT(created_at, '%Y-%m-%d')").
 		Scan(&rows).Error
 	return rows, err
 }
@@ -403,7 +403,7 @@ func (r *Repository) dailySettlements(ctx context.Context, query DashboardQuery)
 	db := r.db.WithContext(ctx)
 	rows := make([]dailySettlementRow, 0)
 	err := db.Table("rental_orders AS ro").
-		Select(`DATE(ro.settled_at) AS date,
+		Select(`DATE_FORMAT(ro.settled_at, '%Y-%m-%d') AS date,
 					COALESCE(SUM(oc.platform_fee_cent), 0) AS platform_income_amount_cent,
 					COALESCE(SUM(oc.owner_income_amount_cent), 0) AS owner_should_income_amount_cent,
 					COALESCE(SUM(COALESCE(w.owner_wallet_income_amount_cent, 0)), 0) AS owner_wallet_income_amount_cent,
@@ -445,7 +445,7 @@ func (r *Repository) dailySettlements(ctx context.Context, query DashboardQuery)
 		Joins("JOIN order_checkouts AS oc ON oc.order_id = ro.id AND oc.status = 'accepted'").
 		Joins("LEFT JOIN (?) AS w ON w.order_id = ro.id", ownerWalletIncomeForSettledOrdersSubquery(db, query)).
 		Where("ro.settled_at >= ? AND ro.settled_at <= ?", query.StartDate, query.EndDate).
-		Group("DATE(ro.settled_at)").
+		Group("DATE_FORMAT(ro.settled_at, '%Y-%m-%d')").
 		Scan(&rows).Error
 	return rows, err
 }
@@ -521,7 +521,7 @@ func (r *Repository) dailyPayments(ctx context.Context, query DashboardQuery) ([
 	rows := make([]dailyPaymentRow, 0)
 	db := r.db.WithContext(ctx)
 	err := db.Table("payment_orders AS po").
-		Select(`DATE(po.created_at) AS date,
+		Select(`DATE_FORMAT(po.created_at, '%Y-%m-%d') AS date,
 			COALESCE(SUM(CASE WHEN po.biz_type IN ? AND po.status = 'paid' THEN po.amount_cent ELSE 0 END), 0) AS total_flow_amount_cent,
 			COALESCE(SUM(CASE WHEN po.biz_type IN ? AND po.status = 'refunded' THEN po.amount_cent ELSE 0 END), 0) AS total_refund_amount_cent,
 			COALESCE(SUM(CASE WHEN po.biz_type IN ? AND po.status = 'refunding' THEN po.amount_cent ELSE 0 END), 0) AS pending_refund_amount_cent,
@@ -536,7 +536,7 @@ func (r *Repository) dailyPayments(ctx context.Context, query DashboardQuery) ([
 			payBizTypes(), refundBizTypes(), refundBizTypes(), payBizTypes(), refundBizTypes(), refundBizTypes(), refundBizTypes(), normalRefundBizTypes()).
 		Joins("LEFT JOIN (?) AS orig ON orig.order_id = po.order_id", paymentOriginalAmountForRefundsInRangeSubquery(db, query)).
 		Where("po.created_at >= ? AND po.created_at <= ?", query.StartDate, query.EndDate).
-		Group("DATE(po.created_at)").
+		Group("DATE_FORMAT(po.created_at, '%Y-%m-%d')").
 		Scan(&rows).Error
 	return rows, err
 }
@@ -545,10 +545,10 @@ func (r *Repository) dailyPayments(ctx context.Context, query DashboardQuery) ([
 func (r *Repository) dailyPickupCancelled(ctx context.Context, query DashboardQuery) ([]dailyPickupCancelledRow, error) {
 	rows := make([]dailyPickupCancelledRow, 0)
 	err := r.db.WithContext(ctx).Table("admin_pickups").
-		Select(`DATE(cancelled_at) AS date, COUNT(id) AS count`).
+		Select(`DATE_FORMAT(cancelled_at, '%Y-%m-%d') AS date, COUNT(id) AS count`).
 		Where("status = ?", "cancelled").
 		Where("cancelled_at >= ? AND cancelled_at <= ?", query.StartDate, query.EndDate).
-		Group("DATE(cancelled_at)").
+		Group("DATE_FORMAT(cancelled_at, '%Y-%m-%d')").
 		Scan(&rows).Error
 	return rows, err
 }
@@ -557,15 +557,15 @@ func (r *Repository) dailyPickupCancelled(ctx context.Context, query DashboardQu
 func (r *Repository) dailyPaidOrders(ctx context.Context, query DashboardQuery) ([]dailyPaidOrderRow, error) {
 	items := make([]dailyPaidOrderRow, 0)
 	err := r.db.WithContext(ctx).Table(`(
-		SELECT DATE(paid_at) AS date, COUNT(DISTINCT order_id) AS paid_order_count
+		SELECT DATE_FORMAT(paid_at, '%Y-%m-%d') AS date, COUNT(DISTINCT order_id) AS paid_order_count
 		FROM payment_orders
 		WHERE biz_type = 'order_pay' AND status = 'paid' AND paid_at >= ? AND paid_at <= ?
-		GROUP BY DATE(paid_at)
+		GROUP BY DATE_FORMAT(paid_at, '%Y-%m-%d')
 		UNION ALL
-		SELECT DATE(completed_at) AS date, COUNT(id) AS paid_order_count
+		SELECT DATE_FORMAT(completed_at, '%Y-%m-%d') AS date, COUNT(id) AS paid_order_count
 		FROM admin_pickups
 		WHERE status = 'completed' AND completed_at >= ? AND completed_at <= ?
-		GROUP BY DATE(completed_at)
+		GROUP BY DATE_FORMAT(completed_at, '%Y-%m-%d')
 	) AS daily_paid_orders`, query.StartDate, query.EndDate, query.StartDate, query.EndDate).
 		Select("date, SUM(paid_order_count) AS paid_order_count").
 		Group("date").