chanserv: topic, invite, akick, list, status

Adds the remaining moderation and listing commands. Auto-kick masks are
stored in the event log and enforced on join: a matching user is banned
and kicked. Topic and invite are sourced from the ChanServ pseudoclient.

modules/chanserv/topic.rs

@@ -0,0 +1,16 @@
+use crate::engine::db::Db;
+use crate::engine::service::{Sender, ServiceCtx};
+
+// TOPIC <#channel> <text>: set the channel topic (empty clears it).
+pub fn handle(me: &str, from: &Sender, args: &[&str], ctx: &mut ServiceCtx, db: &Db) {
+    let Some(&chan) = args.get(1) else {
+        ctx.notice(me, from.uid, "Syntax: TOPIC <#channel> <text>");
+        return;
+    };
+    if !super::require_op(me, from, chan, ctx, db) {
+        return;
+    }
+    let text = if args.len() > 2 { args[2..].join(" ") } else { String::new() };
+    ctx.topic(me, chan, &text);
+    ctx.notice(me, from.uid, format!("Topic for \x02{chan}\x02 updated."));
+}