feat: hls content encoding support and shared session between different targets (#789)

* feat: key shared hls sessions by origin id
* feat: support hls content encoding
* fix: coderabbitai findings
* Fix: Custom headers are lost on provider://
In the manual redirect path, the abstract provider:// URL is compared against the resolved HTTP URL.
This causes the request to be marked as "scrubbed" before the first real redirect even occurs, stripping out headers like X-API-Key.

backend/src/api/model/hls_cache/map.rs

@@ -1,6 +1,6 @@
 use super::{cache::MapCacheKey, ids::ProxySessionId, session::HlsSession, timeline::CacheAccessState};
-use axum::http::StatusCode;
 use crate::processing::parser::hls::origin_manifest::ParsedByteRange;
+use axum::http::StatusCode;
 use std::{
     fmt,
     hash::{Hash, Hasher},