OperServ: SHUN and CHANKILL

- SHUN <user@host> silences a matching user network-wide without
  disconnecting them — another kind ("SHUN") in the generalized X-line
  handler (m_shun is loaded), same event-sourced list and lazy expiry as
  AKILL/SQLINE/SNLINE.
- CHANKILL <#channel> [reason] AKILLs every distinct member host in one
  shot to clear a spam or attack channel; the G-lines the ircd applies
  also kill the sessions. Deduped by host, and never bans the operator who
  ran it. Both admin-only.

operserv/src/chankill.rs

@@ -0,0 +1,38 @@
+use fedserv_api::{NetView, Priv, Sender, ServiceCtx, Store};
+use std::collections::HashSet;
+
+// CHANKILL <#channel> [reason]: AKILL every user in a channel by host, clearing
+// a spam or attack channel in one shot. The G-lines the ircd applies also kill
+// the matching sessions. Admin-only, and never bans the operator running it.
+pub fn handle(me: &str, from: &Sender, args: &[&str], ctx: &mut ServiceCtx, net: &dyn NetView, db: &mut dyn Store) {
+    if !from.privs.has(Priv::Admin) {
+        ctx.notice(me, from.uid, "Access denied — CHANKILL needs the \x02admin\x02 privilege.");
+        return;
+    }
+    let Some(&chan) = args.get(1).filter(|c| c.starts_with('#') || c.starts_with('&')) else {
+        ctx.notice(me, from.uid, "Syntax: CHANKILL <#channel> [reason]");
+        return;
+    };
+    let members = net.channel_members(chan);
+    if members.is_empty() {
+        ctx.notice(me, from.uid, format!("No one is in \x02{chan}\x02 (or it isn't tracked)."));
+        return;
+    }
+    let reason = if args.len() > 2 { args[2..].join(" ") } else { "Channel cleared by services".to_string() };
+    let setter = from.account.unwrap_or(from.nick);
+    let mut seen: HashSet<String> = HashSet::new();
+    let mut banned = 0;
+    for uid in &members {
+        if uid.as_str() == from.uid {
+            continue; // never ban yourself
+        }
+        let Some(host) = net.host_of(uid) else { continue };
+        if seen.insert(host.to_string()) {
+            let mask = format!("*@{host}");
+            let _ = db.akill_add("G", &mask, setter, &reason, None);
+            ctx.add_line("G", &mask, from.nick, 0, &reason);
+            banned += 1;
+        }
+    }
+    ctx.notice(me, from.uid, format!("CHANKILL on \x02{chan}\x02: \x02{banned}\x02 host(s) AKILL'd."));
+}