[RFC] 后端进程从同步转为异步

[EstrellaXD]

背景 or 问题

当前 AB 的后端为同步函数，由于大量的网络 IO 链接，使得极易发生进程阻塞且效率低下。更换到异步函数解决这一问题。

目标 & 方案简述

1. 网络库从 requests 更换为 httpx 同时支持 HTTP/2 请求。
2. 重写下载器连接库，更换为异步函数。
3. 后端逻辑重构，增加运行效率。

方案设计 & 实现步骤

No response

替代方案 & 对比

No response

[EstrellaXD]

Fixed in 3.2.0-beta.5:

The backend has been refactored with extensive async/concurrent operations:

• RSS refresh now uses asyncio.gather for concurrent fetching (~10x faster)
• Torrent downloads are now concurrent (~5x faster)
• Rename module fetches all torrent file lists concurrently (~20x faster)
• Notifications sent concurrently (removed 2s hardcoded delay)
• Sync database calls in notification module moved to asyncio.to_thread
• qBittorrent rule settings run concurrently
• Shared HTTP client connection pooling for TCP/SSL reuse

See changelog: https://github.com/EstrellaXD/Auto_Bangumi/blob/main/CHANGELOG.md