【性能调优】定时器合并：同频任务的统一调度

---同频定时器的统一调度
local Scheduler = { buckets = {} }

---注册：按间隔分桶
function Scheduler.every(interval, name, fn)
    local b = Scheduler.buckets[interval] or
        { fns = {}, next = os.time() + interval }
    b.fns[name] = fn
    Scheduler.buckets[interval] = b
end

---引擎侧每秒的驱动器（唯一）
setontimerex(100, 1)
function Scheduler.tick()
    local now = os.time()
    for interval, b in pairs(Scheduler.buckets) do
        if now >= b.next then
            b.next = now + interval
            for name, fn in pairs(b.fns) do
                local ok, err = pcall(fn)
                if not ok then
                    Ops.alert("任务异常: " .. name ..
                        " " .. tostring(err))
                end
            end
        end
    end
end

---任务的注册与自检
Scheduler.every(300, "mail_expire", Mail.expireScan)
Scheduler.every(300, "friend_clean", Friend.cleanRequests)
Scheduler.every(3600, "backup_check", Backup.verify)

---同频任务的自检：任务清单的健康度
setontimerex(101, 1800)
function Scheduler.selfcheck()
    for interval, b in pairs(Scheduler.buckets) do
        local n = 0
        for _ in pairs(b.fns) do n = n + 1 end
        -- 单桶任务超过 50 个提示分桶
        if n > 50 then
            Ops.alert("桶任务过多: " .. interval ..
                "s 共 " .. n .. " 个")
        end
    end
end