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.

Cargo.lock

@@ -1383,6 +1383,9 @@ dependencies = [
  "futures-util",
  "hive-claude",
  "hive-sh4re",
+ "http-body-util",
+ "hyper",
+ "hyper-util",
  "reqwest",
  "rmcp",
  "rusqlite",