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/nodes/handler_grpc.go

@@ -293,7 +293,7 @@ func (h *Handler) ReportUsage(ctx context.Context, req *agentv1.UsageReport) (*a
 		if entry.DpUUID == "" {
 			continue
 		}
-		userID, found, err := h.store.UserIDByDpUUID(ctx, entry.DpUUID)
+		userID, deviceID, found, err := h.store.UserDeviceByDpUUID(ctx, entry.DpUUID)
 		if err != nil {
 			slog.Warn("nodes.Handler.ReportUsage: dp_uuid lookup failed",
 				"dp_uuid", entry.DpUUID, "err", err)
@@ -302,12 +302,23 @@ func (h *Handler) ReportUsage(ctx context.Context, req *agentv1.UsageReport) (*a
 		if !found {
 			continue
 		}
+		// Account-level rollup (always).
 		if err := h.store.AccumulateUsage(ctx, userID, date,
 			entry.BytesUp, entry.BytesDown, entry.SessionMinutes,
 		); err != nil {
 			slog.Warn("nodes.Handler.ReportUsage: accumulate failed",
 				"user_id", userID, "err", err)
 		}
+		// Per-device attribution (only when the dp_uuid maps to a registered device;
+		// deviceID==0 means a legacy account-level credential — no device dimension).
+		if deviceID > 0 {
+			if err := h.store.AccumulateDeviceUsage(ctx, userID, deviceID, date,
+				entry.BytesUp, entry.BytesDown, entry.SessionMinutes,
+			); err != nil {
+				slog.Warn("nodes.Handler.ReportUsage: device accumulate failed",
+					"user_id", userID, "device_id", deviceID, "err", err)
+			}
+		}
 	}
 	return &agentv1.UsageAck{}, nil
 }