Fetches refuse internal addresses unless fetch_internal lists them (#320)

ipx's clients had no destination policy and followed redirects
anywhere. Adding a feed returned the status or first line of whatever
answered at the address; an enclosure declared as audio was downloaded
whole from any URL and served back through /media; /api/art fetched
any image a feed named. Feeds come from publishers and anyone signed
in, so loopback, the Docker network and the LAN were all reachable.

ipx-feed's guard is a connector layer: after the name resolves and the
connection opens, before the request is written, it looks at the
peer's address and refuses anything off the public internet unless
config.toml's [general] fetch_internal lists it. Being on the
connection, it covers every request on ctx.client and feed_client,
each redirect hop, IP literals (which never reach a DNS resolver) and
a name that resolves differently the second time. reqwest's rustls
connection reports the peer address; a test run by hand checks HTTPS
gets through, since were it lost every https fetch would be refused.

The directory is on the server's own network by design
(http://ipx-directory:8100), so it moves to local_client, unguarded,
set by an admin. The browser suite and load tests serve their feeds on
loopback and list 127.0.0.1.

Not covered: librqbit's own connections (trackers, peers), which do
not go through these clients.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

Cargo.toml

@@ -27,6 +27,8 @@ opentelemetry_sdk = { version = "0.33", default-features = false, features = ["t
 opml = "1.1.6"
 pulldown-cmark = { version = "0.13.4", default-features = false, features = ["html"] }
 mimalloc = "0.1.52"
+http = "1.5.0"
+hyper-util = { version = "0.1.20", features = ["client-legacy"] }
 percent-encoding = "2.3.2"
 quick-xml = { version = "0.42.0", features = ["escape-html"] }
 reqwest = { version = "0.13.5", default-features = false, features = ["rustls", "http2", "gzip", "brotli", "zstd", "stream", "json", "charset", "system-proxy"] }