feat: 精确耗电计算(接入充值记录接口)

- 新增 queryISIMSRoomBuyRecord 充值记录获取 + 10分钟缓存

- 日耗电 = 剩余变化 + 当天充值电量(电价0.535元/度)

- 月度汇总增加充值次数/电量/金额

Ultraworked with [Sisyphus](https://github.com/code-yeongyu/oh-my-openagent)

Co-authored-by: Sisyphus <clio-agent@sisyphuslabs.ai>

go/buy_records.go

@@ -0,0 +1,118 @@
+package main
+
+import (
+	"encoding/json"
+	"fmt"
+	"strings"
+	"time"
+)
+
+// buy_records.go - 充值/缴费记录获取与缓存
+// 接口: POST /app/electric/queryISIMSRoomBuyRecord
+// 返回每笔充值记录(金额/类型/时间)，用于精确计算日耗电
+
+// buyRecord 单笔充值记录
+type buyRecord struct {
+	Date   string  `json:"date"`    // 充值日期 YYYY-MM-DD
+	Money  float64 `json:"money"`   // 充值金额(元)
+	Kwh    float64 `json:"kwh"`     // 换算电量(度) = money / price
+	Type   string  `json:"type"`    // 现金充值 / 下发补助
+	Detail string  `json:"detail"`  // 完整时间 YYYY-M-D H:M:S
+}
+
+// 充值记录缓存
+var (
+	buyRecordsCache []buyRecord
+	buyRecordsTime  int64
+)
+
+// queryBuyRecords 获取某房间的充值记录（需 application 域 shiroJID）
+func queryBuyRecords(shiroJID string, room *roomInfo) ([]buyRecord, error) {
+	price := unitPrice()
+	s := newXfSession(shiroJID)
+	body := fmt.Sprintf("areaId=%s&buildingCode=%s&floorCode=%s&roomCode=%s&mdtype=room&platform=%s",
+		room.AreaID, room.BuildingCode, room.FloorCode, room.RoomCode, xfPlatform)
+	b, _, err := s.postForm("https://application.xiaofubao.com/app/electric/queryISIMSRoomBuyRecord",
+		body, "https://application.xiaofubao.com/")
+	if err != nil {
+		return nil, err
+	}
+	var res struct {
+		StatusCode flexInt `json:"statusCode"`
+		Rows       []struct {
+			DateTime  string `json:"datetime"`   // "2026-8-23 0:45:49"
+			BuyType   string `json:"buytype"`    // 现金充值 / 下发补助
+			BuyUsing  string `json:"buyusingtpe"` // 照明用电
+			Money     string `json:"money"`      // "40.00"
+		} `json:"rows"`
+	}
+	if err := json.Unmarshal(b, &res); err != nil {
+		return nil, err
+	}
+	if res.StatusCode != 0 {
+		return nil, fmt.Errorf("queryISIMSRoomBuyRecord 失败: %s", string(b))
+	}
+
+	var records []buyRecord
+	for _, r := range res.Rows {
+		var money float64
+		fmt.Sscanf(r.Money, "%f", &money)
+		rec := buyRecord{
+			Date:   datePart(r.DateTime),
+			Money:  round2(money),
+			Kwh:    round2(money / price),
+			Type:   r.BuyType,
+			Detail: r.DateTime,
+		}
+		records = append(records, rec)
+	}
+	return records, nil
+}
+
+// getBuyRecordsCached 获取充值记录（带缓存，10 分钟有效）
+func getBuyRecordsCached(shiroJID string, room *roomInfo) ([]buyRecord, error) {
+	if buyRecordsCache != nil && time.Now().Unix()-buyRecordsTime < 600 {
+		return buyRecordsCache, nil
+	}
+	recs, err := queryBuyRecords(shiroJID, room)
+	if err != nil {
+		return nil, err
+	}
+	buyRecordsCache = recs
+	buyRecordsTime = time.Now().Unix()
+	return recs, nil
+}
+
+// rechargeKwhByDate 生成 map[date] -> 当天充值电量(度)
+func rechargeKwhByDate(records []buyRecord) map[string]float64 {
+	m := map[string]float64{}
+	for _, r := range records {
+		m[r.Date] = round2(m[r.Date] + r.Kwh)
+	}
+	return m
+}
+
+// unitPrice 电价（元/度），默认 0.535，可用 XF_PRICE 环境变量覆盖
+func unitPrice() float64 {
+	if v := envOr("XF_PRICE", ""); v != "" {
+		var p float64
+		if _, err := fmt.Sscanf(v, "%f", &p); err == nil && p > 0 {
+			return p
+		}
+	}
+	return 0.535
+}
+
+// datePart 从 "2026-8-23 0:45:49" 提取 "2026-08-23"
+func datePart(dt string) string {
+	parts := strings.SplitN(dt, " ", 2)
+	if len(parts) == 0 {
+		return dt
+	}
+	// 规范化月份/日补零
+	ymd := strings.Split(parts[0], "-")
+	if len(ymd) != 3 {
+		return parts[0]
+	}
+	return fmt.Sprintf("%s-%02s-%02s", ymd[0], ymd[1], ymd[2])
+}