fix(backend): 财务汇总 500（only_full_group_by 预处理协议回归）+ summary 加 draft_count

- /finance/summary：SEC-001 给 JOIN 加 shop_id 条件后，MySQL 预处理协议推导不出
  p.name 函数依赖 → 1055（文本协议可过，CLI 无法复现）。GROUP BY 补 p.name 修复，
  并给该 handler 加错误日志（此前吞错致排查困难）。v1.0.85 起全店受影响。
- 出入库 summary 新增 draft_count（草稿单数 KPI 卡数据源）。

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01JJ1g8XV1YhhmHRzhwWEW7o

backend/internal/handler/stock_out.go

@@ -117,6 +117,8 @@ func (h *StockOutHandler) Summary(c *gin.Context) {
 	s.LastMonthCount, s.LastMonthAmount = agg(prevFrom, prevTo)
 	h.db.Model(&model.StockOutOrder{}).
 		Where("shop_id = ? AND status = ? AND deleted_at IS NULL", shopID, "pending").Count(&s.PendingCount)
+	h.db.Model(&model.StockOutOrder{}).
+		Where("shop_id = ? AND status = ? AND deleted_at IS NULL", shopID, "draft").Count(&s.DraftCount)
 	c.JSON(http.StatusOK, s)
 }