feat(stats): #10 第②层 —— 统计页按设备过滤(per-device 本地日曲线)

镜像账户级时区曲线到「按设备」:
- migration 000018 `usage_device_hourly`(每设备 UTC 小时桶,稀疏)。
- ReportUsage deviceID>0 时加 AccumulateDeviceHourly;NodeStore 接口+impl+mock。
- usage.Store.DeviceHourlyRange(JOIN devices 校验归属+解析 uuid→id);UsageCurve
  增 deviceUUID 形参:空=账户级,非空=该设备本地日曲线(分桶逻辑复用)。
- /v1/usage?device=<uuid>;客户端 account_api.usage(device)、usageProvider key 改
  记录 (days,device)、stats_page 接 statsDeviceProvider → 选设备即重取该设备曲线。
测试:per-device 曲线隔离+归属校验(A的设备不进B)、UsageCurve(deviceUUID)、
migration v18、客户端 widget(选设备→/v1/usage 带 device=)。全量 go/flutter 绿。

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

server/internal/nodes/grpc_test.go

@@ -132,6 +132,12 @@ func (m *mockNodeStore) AccumulateHourly(_ context.Context, userID int64, hour t
 	return nil
 }
 
+func (m *mockNodeStore) AccumulateDeviceHourly(_ context.Context, _, _ int64, _ time.Time,
+	_, _, _ int64,
+) error {
+	return nil
+}
+
 func (m *mockNodeStore) EnsureDeviceDpUUID(_ context.Context, _ int64, _ string) (string, int64, error) {
 	return "", 0, nil
 }

server/internal/nodes/handler_grpc.go

@@ -325,6 +325,13 @@ func (h *Handler) ReportUsage(ctx context.Context, req *agentv1.UsageReport) (*a
 				slog.Warn("nodes.Handler.ReportUsage: device accumulate failed",
 					"user_id", userID, "device_id", deviceID, "err", err)
 			}
+			// Per-device hourly (tz-aware per-device display curve, #10②).
+			if err := h.store.AccumulateDeviceHourly(ctx, userID, deviceID, windowEnd,
+				entry.BytesUp, entry.BytesDown, entry.SessionMinutes,
+			); err != nil {
+				slog.Warn("nodes.Handler.ReportUsage: device hourly accumulate failed",
+					"user_id", userID, "device_id", deviceID, "err", err)
+			}
 			// Heartbeat: keep the device's "online" status fresh while it reports.
 			if err := h.store.TouchDeviceLastSeen(ctx, deviceID); err != nil {
 				slog.Warn("nodes.Handler.ReportUsage: touch last_seen failed",

server/internal/nodes/store.go

@@ -108,6 +108,12 @@ type NodeStore interface {
 	AccumulateDeviceUsage(ctx context.Context, userID, deviceID int64, date time.Time,
 		bytesUp, bytesDown int64, minutes int64) error
 
+	// AccumulateDeviceHourly adds bytes/minutes to usage_device_hourly keyed by
+	// (deviceID, UTC epoch hour) — the per-device counterpart of AccumulateHourly,
+	// for timezone-aware per-device day bucketing at query time.
+	AccumulateDeviceHourly(ctx context.Context, userID, deviceID int64, hour time.Time,
+		bytesUp, bytesDown int64, minutes int64) error
+
 	// TouchDeviceLastSeen bumps devices.last_seen to now for an active device,
 	// driving the "online" status (connect + periodic usage reports refresh it).
 	TouchDeviceLastSeen(ctx context.Context, deviceID int64) error
@@ -501,3 +507,23 @@ func (s *SQLNodeStore) AccumulateHourly(
 	}
 	return nil
 }
+
+// AccumulateDeviceHourly adds bytes/minutes to usage_device_hourly for
+// (deviceID, UTC epoch hour). Per-device counterpart of AccumulateHourly.
+func (s *SQLNodeStore) AccumulateDeviceHourly(
+	ctx context.Context, userID, deviceID int64, hour time.Time,
+	bytesUp, bytesDown int64, minutes int64,
+) error {
+	h := hour.UTC().Unix() / 3600
+	q := `
+		INSERT INTO usage_device_hourly (user_id, device_id, hour, bytes_up, bytes_down, minutes_used)
+		VALUES (?, ?, ?, ?, ?, ?)
+		` + s.dialect.Upsert([]string{"device_id", "hour"},
+		"bytes_up = bytes_up + EXCLUDED.bytes_up",
+		"bytes_down = bytes_down + EXCLUDED.bytes_down",
+		"minutes_used = minutes_used + EXCLUDED.minutes_used")
+	if _, err := s.db.ExecContext(ctx, q, userID, deviceID, h, bytesUp, bytesDown, minutes); err != nil {
+		return fmt.Errorf("nodes.SQLNodeStore.AccumulateDeviceHourly: %w", err)
+	}
+	return nil
+}