feat(server/stats): stats-overhaul Phase2 — 每设备归因 + GB 综合配额

服务端记账从「账户」细到「每设备」(每设备独立 dp_uuid),配额单位分钟→GB
按账户综合卡控。000015_per_device_usage 迁移(mysql+sqlite 双份):devices.dp_uuid
+ usage_device_daily 表 + plans.daily_mb。handler_grpc 按 dp_uuid 回映射
(user_id,device_id) 双写账户+每设备;usage 服务/handler 暴露 /v1/usage(/devices)。
含 sqlite_per_device / usage handler 测试。

注:此迁移 prod 已 migrate up 运行、部署二进制已内嵌;本次补提交使 git 与线上一致。

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

server/internal/usage/service.go

@@ -85,6 +85,49 @@ func (svc *Service) UsageCurve(ctx context.Context, userID int64, days int) ([]U
 	return points, nil
 }
 
+// DeviceUsagePoint is one device's aggregated usage over the requested window,
+// used by the stats page's per-device ("下分设备") breakdown.
+type DeviceUsagePoint struct {
+	UUID        string `json:"uuid"`
+	Name        string `json:"name"`
+	Platform    string `json:"platform"` // ios | android | windows | macos
+	BytesUp     uint64 `json:"bytes_up"`
+	BytesDown   uint64 `json:"bytes_down"`
+	MinutesUsed int    `json:"minutes_used"`
+}
+
+// DeviceUsage returns per-device usage totals for userID over the last `days`
+// (UTC), busiest device first.  days is clamped to [1, 90].  Devices with no
+// usage in the window are omitted (the response is never nil — empty slice).
+func (svc *Service) DeviceUsage(ctx context.Context, userID int64, days int) ([]DeviceUsagePoint, *apierr.Error) {
+	if days < 1 {
+		days = 7
+	}
+	if days > 90 {
+		days = 90
+	}
+
+	today := utcToday()
+	from := today.AddDate(0, 0, -(days - 1))
+
+	rows, err := svc.store.DeviceUsageRange(ctx, userID, from, today)
+	if err != nil {
+		return nil, apierr.ErrInternal
+	}
+	points := make([]DeviceUsagePoint, 0, len(rows))
+	for _, r := range rows {
+		points = append(points, DeviceUsagePoint{
+			UUID:        r.UUID,
+			Name:        r.Name,
+			Platform:    r.Platform,
+			BytesUp:     r.BytesUp,
+			BytesDown:   r.BytesDown,
+			MinutesUsed: r.MinutesUsed,
+		})
+	}
+	return points, nil
+}
+
 // TodaySummary is the /v1/me today_usage block.
 type TodaySummary struct {
 	MinutesUsed      int  `json:"minutes_used"`