【数据存储】跨服战报的归档：赛季数据的冷热分层

---战报的分层写入
function WarReport.store(report)
    if report.season == currentSeason then
        hotStore[#hotStore + 1] = report
    else
        ColdArchive.write(report.season, report)
    end
end

---赛季结束的批量转冷
function WarReport.freeze(season)
    local reports = hotStore.bySeason(season)
    ColdArchive.bulkWrite(season, reports)
    for i = #hotStore, 1, -1 do
        if hotStore[i].season == season then table.remove(hotStore, i) end
    end
end

---冷数据的检索：按玩家与赛季过滤
function WarReport.coldQuery(userId, season)
    local archive = ColdArchive.load(season)
    local out = {}
    for _, rep in ipairs(archive) do
        if rep.userId == userId then out[#out + 1] = rep end
    end
    return out
end