web_ui: support unix:<path> upstreams in extraWebProxies

reqwest has no UDS transport, so unix: upstreams dial the socket
directly with a raw hyper/1.1 client per request instead. http(s)://
upstreams are unaffected (still go through the existing reqwest path).

Adds hyper (client, http1), hyper-util (tokio IO adapter), and
http-body-util as direct hive-ag3nt dependencies - all three were
already present transitively via reqwest, this just uses them
directly for the new code path.

hive-ag3nt/Cargo.toml

@@ -10,6 +10,9 @@ workspace = true
 anyhow.workspace = true
 axum.workspace = true
 reqwest.workspace = true
+hyper.workspace = true
+hyper-util.workspace = true
+http-body-util.workspace = true
 forgejo-api.workspace = true
 url.workspace = true
 time.workspace = true