fix: 修复课程表DayOfWeek字段omitzero导致周一数据被省略的问题

internal/dto/schedule_dto.go

@@ -5,7 +5,7 @@ type ScheduleCourseResponse struct {
 	Name         string `json:"name"`
 	Teacher      string `json:"teacher,omitempty"`
 	Location     string `json:"location,omitempty"`
-	DayOfWeek    int    `json:"day_of_week,omitzero"`
+	DayOfWeek    int    `json:"day_of_week"`
 	StartSection int    `json:"start_section,omitzero"`
 	EndSection   int    `json:"end_section,omitzero"`
 	Weeks        []int  `json:"weeks"`