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/dto.go

@@ -499,6 +499,22 @@ type DeviceTokenResponse struct {
 	CreatedAt  time.Time `json:"created_at"`
 }
 
+// AdminDeviceTokenResponse 管理端设备Token响应
+// 相比 DeviceTokenResponse，额外包含 user_id 与 push_token（即 JPush RegistrationID），
+// 供后台查询用户设备 registration_id 使用。
+type AdminDeviceTokenResponse struct {
+	ID         int64     `json:"id"`
+	UserID     string    `json:"user_id"`
+	DeviceID   string    `json:"device_id"`
+	DeviceType string    `json:"device_type"`
+	PushToken  string    `json:"push_token,omitempty"` // JPush RegistrationID
+	IsActive   bool      `json:"is_active"`
+	DeviceName string    `json:"device_name,omitempty"`
+	LastUsedAt time.Time `json:"last_used_at,omitzero"`
+	CreatedAt  time.Time `json:"created_at"`
+	UpdatedAt  time.Time `json:"updated_at"`
+}
+
 // ==================== 推送记录 DTOs ====================
 
 // PushRecordResponse 推送记录响应