first commit, i i have no idea what i have done

server/internal/dto/device.go

@@ -0,0 +1,56 @@
+package dto
+
+import "smoop-api/internal/models"
+
+type DeviceDto struct {
+	GUID  string    `json:"guid"`
+	Name  string    `json:"name"`
+	Users []UserDto `json:"users,omitempty"`
+}
+
+type DeviceListDto struct {
+	Devices []DeviceDto `json:"devices"`
+	Offset  int         `json:"offset"`
+	Limit   int         `json:"limit"`
+	Total   int64       `json:"total"`
+}
+
+type CreateDeviceDto struct {
+	GUID    string `json:"guid" binding:"required"`
+	Name    string `json:"name" binding:"required"`
+	UserIDs []uint `json:"userIds"`
+}
+
+type RenameDeviceDto struct {
+	Name string `json:"name" binding:"required"`
+}
+
+type EditDeviceToUserRelationDto struct {
+	UserID  uint   `json:"userId"`
+	UserIDs []uint `json:"userIds"`
+}
+
+// Remove users: accept one or many (kept separate for clarity of intent)
+type RemoveDeviceUsersDto struct {
+	UserID  uint   `json:"userId"`
+	UserIDs []uint `json:"userIds"`
+}
+
+// Replace users: set entire list (may be empty to clear all)
+type SetDeviceUsersDto struct {
+	UserIDs []uint `json:"userIds"`
+}
+
+func MapDevice(d models.Device) DeviceDto {
+	out := DeviceDto{
+		GUID: d.GUID,
+		Name: d.Name,
+	}
+	if len(d.Users) > 0 {
+		out.Users = make([]UserDto, 0, len(d.Users))
+		for _, u := range d.Users {
+			out.Users = append(out.Users, MapUser(u))
+		}
+	}
+	return out
+}