Clippy sweep: clean across the workspace

- Box the oversized enum variants (Event::AccountRegistered, gossip
  Msg::Entry) so small events aren't sized to a full Account; serde is
  transparent so the wire/log format is unchanged.
- Use the configured server description in the SERVER line (it was
  hardcoded and the config field went unread).
- Derive the ChanServ SET label from the ChanSetting (drops toggle's 8th
  arg); rename inspircd from_us -> sourced.
- allow the two framework-idiom lints with rationale (tonic's Status in
  authorize; the guest-rename handler's inherent arg count).
- Auto-fixed map_or/contains/split_once style lints.

src/main.rs

@@ -39,6 +39,7 @@ async fn main() -> Result<()> {
 
     let proto = Box::new(InspIrcd::new(
         cfg.server.name.clone(),
+        cfg.server.description.clone(),
         cfg.server.sid.clone(),
         cfg.uplink.password.clone(),
         cfg.server.protocol,