Split InfoServ into one file per command

POST/DEL/LIST each move to their own file (each still parameterised by
bulletin kind, so OPOST/ODEL/OLIST route to the same handler); the kind
constants stay in lib.rs beside the dispatcher. No behaviour change.

modules/infoserv/src/list.rs

@@ -0,0 +1,19 @@
+use fedserv_api::{Sender, ServiceCtx, Store};
+
+// LIST/OLIST: show the bulletins of a kind. Public is open; oper is oper-only.
+pub fn handle(me: &str, from: &Sender, kind: &str, oper_only: bool, ctx: &mut ServiceCtx, db: &mut dyn Store) {
+    if oper_only && !from.privs.any() {
+        ctx.notice(me, from.uid, "Access denied — oper bulletins are for services operators.");
+        return;
+    }
+    let items = db.news(kind);
+    let which = if kind == super::OPER { "oper" } else { "public" };
+    if items.is_empty() {
+        ctx.notice(me, from.uid, format!("There are no {which} bulletins."));
+        return;
+    }
+    for (i, item) in items.iter().enumerate() {
+        ctx.notice(me, from.uid, format!("{}. {} — by {}", i + 1, item.text, item.setter));
+    }
+    ctx.notice(me, from.uid, format!("End of {which} bulletins ({} shown).", items.len()));
+}