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/usage/usage_integration_test.go

@@ -110,6 +110,14 @@ func applySchema(db *sql.DB) error {
 			ad_unlocked_at DATETIME(6) NULL,
 			PRIMARY KEY (user_id, date)
 		) ENGINE=InnoDB DEFAULT CHARSET=utf8mb4`,
+		`CREATE TABLE IF NOT EXISTS usage_hourly (
+			user_id      BIGINT UNSIGNED NOT NULL,
+			hour         BIGINT NOT NULL,
+			bytes_up     BIGINT UNSIGNED NOT NULL DEFAULT 0,
+			bytes_down   BIGINT UNSIGNED NOT NULL DEFAULT 0,
+			minutes_used INT NOT NULL DEFAULT 0,
+			PRIMARY KEY (user_id, hour)
+		) ENGINE=InnoDB DEFAULT CHARSET=utf8mb4`,
 		`INSERT IGNORE INTO plans (code, max_devices, daily_minutes, ad_gate)
 		 VALUES ('free',1,10,TRUE), ('pro',5,NULL,FALSE), ('team',10,NULL,FALSE)`,
 	}
@@ -445,7 +453,7 @@ func TestIntUsageCurveZeroFill(t *testing.T) {
 	db.Exec(`INSERT INTO usage_hourly (user_id, hour, bytes_up, bytes_down, minutes_used) VALUES (?,?,?,?,?)`,
 		uid, epochHour(today.AddDate(0, 0, -3)), 50, 60, 2)
 
-	points, apiErr := svc.UsageCurve(context.Background(), uid, 7, 0)
+	points, apiErr := svc.UsageCurve(context.Background(), uid, 7, 0, "")
 	if apiErr != nil {
 		t.Fatalf("curve: %v", apiErr)
 	}
@@ -486,7 +494,7 @@ func TestIntUsageCurveOnlyCurrentUser(t *testing.T) {
 	db.Exec(`INSERT INTO usage_hourly (user_id, hour, bytes_up, bytes_down, minutes_used) VALUES (?,?,?,?,?)`, uA, h, 111, 0, 1)
 	db.Exec(`INSERT INTO usage_hourly (user_id, hour, bytes_up, bytes_down, minutes_used) VALUES (?,?,?,?,?)`, uB, h, 999, 0, 9)
 
-	points, _ := svc.UsageCurve(context.Background(), uA, 1, 0)
+	points, _ := svc.UsageCurve(context.Background(), uA, 1, 0, "")
 	if len(points) != 1 || points[0].BytesUp != 111 {
 		t.Errorf("user A curve leaked other user data: %+v", points)
 	}