OperServ: INFO staff notes on accounts and channels

INFO ADD <target> <note> / DEL <target> / <target> attaches a staff note
to an account or channel (a #name is a channel, else an account). The note
is shown in that service's INFO — but to operators only (Priv::Auspex),
never to the account's own owner. Admin-only to set.

Follows the typed-field-on-the-entity pattern: an oper_note field folded
through AccountOperNoteSet (Global) / ChannelOperNoteSet (Local) events,
read via dedicated Store getters so it stays out of the public views and
the directory feed.

nickserv/src/info.rs

@@ -31,4 +31,10 @@ pub fn handle(me: &str, from: &Sender, args: &[&str], ctx: &mut ServiceCtx, db:
             ctx.notice(me, from.uid, format!("  Auto-join  : {} channel(s) — see \x02AJOIN LIST\x02", ajoin.len()));
         }
     }
+    // A staff note is for operators' eyes only, never the account's owner.
+    if from.privs.has(Priv::Auspex) {
+        if let Some(note) = db.account_note(&acct.name) {
+            ctx.notice(me, from.uid, format!("  Staff note : {note}"));
+        }
+    }
 }