dsh-sidebar-downloads: aria2 Download Progress Sidebar View

`dsh-sidebar-downloads` is a companion plugin for `dsh-better-sidebar`, designed to integrate aria2 download progress as a dedicated page within the DSH sidebar, solving the issue of floating windows covering content. The plugin reads the task ledger and uses aria2 RPC to provide real-time data corrections, offering features such as real-time progress, speed, remaining time, and history management. It supports displaying downloads with unknown sizes, automatically cleaning up invalid records, and expanding details, and is intended to be used together with `dsh-download-guard`. Installation depends on `dsh-better-sidebar`, and configuring `ARIA2_RPC_HOST` and `PORT` enables it to connect to the local aria2 engine.