👑[Enhancement] 增加轻量模式，后台运行释放内存Add a lightweight mode to release memory when running in the background

### 🥰 需求描述(Description)

watt太吃内存了，只开启加速的时候就要消耗掉100MB内存
Watt consumes too much memory; it uses up 100MB of memory just when acceleration is enabled.

这相当于我flclash的全部内存。
This is equivalent to all the memory of my flclash
但是令我非常迷惑的是，为什么开启了图形界面之后再关闭就不能回收内存呢？它居然要消耗我300MB内存，即使关闭之后也不会释放UI界面的内存，就硬生生一直占用。
But what confuses me greatly is, why can't memory be reclaimed after turning on the graphical interface and then turning it off? It actually consumes 300MB of my memory, and even after being turned off, it won't release the UI interface's memory, just occupying it persistently.

### 🧐 解决方案(Solution)

减小内存消耗，降低让后台运行时候的内存消耗；在关闭ui界面后，及时释放UI界面占用的内存
Reduce memory consumption, lower the memory usage when running in the background; promptly release the memory occupied by the UI interface after closing it.

No file, test, or entry point is named. Start by reproducing memory usage with acceleration enabled, then after opening and closing the graphical interface, profile the background process and UI lifetime. Done means background operation uses less memory and closing the UI releases its retained memory.

Written by the indexing model from the issue text.