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/store.go

@@ -107,6 +107,48 @@ func (s *Store) GetUsageRange(ctx context.Context, userID int64, from, to time.T
 	return out, rows.Err()
 }
 
+// DeviceUsageRow is one device's aggregated usage over a date window, joined to
+// the devices table for display metadata.  It is the per-device ("下分设备")
+// counterpart of DailyUsage's account rollup.
+type DeviceUsageRow struct {
+	UUID        string
+	Name        string
+	Platform    string
+	BytesUp     uint64
+	BytesDown   uint64
+	MinutesUsed int
+}
+
+// DeviceUsageRange returns each device's summed usage over [from, to] (inclusive
+// UTC dates) for userID, one row per device, ordered by total bytes descending.
+// Devices with no usage in the window are omitted.  All non-aggregate columns
+// are in GROUP BY for MySQL ONLY_FULL_GROUP_BY portability (sqlite tolerant).
+func (s *Store) DeviceUsageRange(ctx context.Context, userID int64, from, to time.Time) ([]DeviceUsageRow, error) {
+	rows, err := s.db.QueryContext(ctx,
+		`SELECT d.uuid, d.name, d.platform,
+		        SUM(ud.bytes_up), SUM(ud.bytes_down), SUM(ud.minutes_used)
+		 FROM usage_device_daily ud
+		 JOIN devices d ON d.id = ud.device_id
+		 WHERE ud.user_id = ? AND ud.date BETWEEN ? AND ?
+		 GROUP BY ud.device_id, d.uuid, d.name, d.platform
+		 ORDER BY (SUM(ud.bytes_up) + SUM(ud.bytes_down)) DESC`,
+		userID, from.UTC().Format(dateLayout), to.UTC().Format(dateLayout))
+	if err != nil {
+		return nil, fmt.Errorf("store.DeviceUsageRange: %w", err)
+	}
+	defer rows.Close()
+
+	var out []DeviceUsageRow
+	for rows.Next() {
+		var r DeviceUsageRow
+		if err := rows.Scan(&r.UUID, &r.Name, &r.Platform, &r.BytesUp, &r.BytesDown, &r.MinutesUsed); err != nil {
+			return nil, fmt.Errorf("store.DeviceUsageRange scan: %w", err)
+		}
+		out = append(out, r)
+	}
+	return out, rows.Err()
+}
+
 // GetDay returns the usage_daily row for (userID, day), or nil if none exists.
 func (s *Store) GetDay(ctx context.Context, userID int64, day time.Time) (*DailyUsage, error) {
 	var u DailyUsage