feat(protocol): away status, excluded phrases, queue-place requests

Three features the client half-had. SetStatus (28) was only ever sent as
"online" at login, so there was no way to go away; excluded search phrases
(160) were parsed and logged into nowhere, so every client kept spending
searches on queries the server was never going to answer; and a queued
download could answer a peer asking about its place but could never ask
about its own.

Each is now driven end to end: the away status seen by another user, a
refused query on a stub server that announces phrases (soulfind keeps its
filters in a database the suite cannot seed), and a peer's answer landing
on the download as its queue position.

soulseek-rs-lib/src/actor/server_actor.rs

@@ -227,6 +227,8 @@ pub enum ServerMessage {
     CantConnectToPeer {
         token: u32,
     },
+    /// Phrases the server refuses to search for (code 160).
+    ExcludedSearchPhrases(Vec<String>),
 }
 
 pub struct ServerActor {
@@ -692,6 +694,11 @@ impl ServerActor {
                     token,
                 });
             }
+            ServerMessage::ExcludedSearchPhrases(phrases) => {
+                self.forward_to_client(ClientOperation::ExcludedSearchPhrases(
+                    phrases,
+                ));
+            }
             other => {
                 error!("[server] unroutable message: {:?}", other);
             }