feat(admin): add admin endpoint to list user devices with JPush registration IDs

- Add AdminDeviceTokenResponse DTO including push_token (RegistrationID) for push debugging
- Add DeviceTokenToAdminResponse and DeviceTokensToAdminResponse converters
- Inject PushService into AdminUserHandler for retrieving user devices
- Register GET /api/v1/admin/users/:id/devices route for querying target user's device tokens

internal/dto/message_converter.go

@@ -199,3 +199,34 @@ func DeviceTokensToResponse(tokens []*model.DeviceToken) []*DeviceTokenResponse
 	}
 	return result
 }
+
+// DeviceTokenToAdminResponse 将DeviceToken转换为管理端响应（含 registration_id）
+func DeviceTokenToAdminResponse(token *model.DeviceToken) *AdminDeviceTokenResponse {
+	if token == nil {
+		return nil
+	}
+	resp := &AdminDeviceTokenResponse{
+		ID:         token.ID,
+		UserID:     token.UserID,
+		DeviceID:   token.DeviceID,
+		DeviceType: string(token.DeviceType),
+		PushToken:  token.PushToken,
+		IsActive:   token.IsActive,
+		DeviceName: token.DeviceName,
+		CreatedAt:  token.CreatedAt,
+		UpdatedAt:  token.UpdatedAt,
+	}
+	if token.LastUsedAt != nil {
+		resp.LastUsedAt = *token.LastUsedAt
+	}
+	return resp
+}
+
+// DeviceTokensToAdminResponse 将DeviceToken列表转换为管理端响应列表
+func DeviceTokensToAdminResponse(tokens []*model.DeviceToken) []*AdminDeviceTokenResponse {
+	result := make([]*AdminDeviceTokenResponse, 0, len(tokens))
+	for _, token := range tokens {
+		result = append(result, DeviceTokenToAdminResponse(token))
+	}
+	return result
+}