Split BotServ and MemoServ into one-file-per-command modules

Match the NickServ/ChanServ layout: lib.rs keeps only the service struct
and the on_command dispatcher, and each command moves to its own file
bridged with #[path]. No behaviour change.

BotServ: bot.rs, assign.rs.
MemoServ: send.rs, list.rs, read.rs, del.rs.

memoserv/src/list.rs

@@ -0,0 +1,26 @@
+use fedserv_api::{human_time, Sender, ServiceCtx, Store};
+
+// LIST: show every memo with a one-line preview; \x02*\x02 marks unread.
+pub fn handle(me: &str, from: &Sender, account: &str, ctx: &mut ServiceCtx, db: &dyn Store) {
+    let memos = db.memo_list(account);
+    if memos.is_empty() {
+        ctx.notice(me, from.uid, "You have no memos.");
+        return;
+    }
+    let unread = memos.iter().filter(|m| !m.read).count();
+    ctx.notice(me, from.uid, format!("Your memos ({} total, {unread} new). \x02*\x02 marks unread:", memos.len()));
+    for (i, m) in memos.iter().enumerate() {
+        let flag = if m.read { ' ' } else { '*' };
+        ctx.notice(me, from.uid, format!("  {}{flag} from \x02{}\x02 ({}): {}", i + 1, m.from, human_time(m.ts), preview(&m.text)));
+    }
+}
+
+// First line / first 80 chars, for LIST.
+fn preview(text: &str) -> String {
+    let line = text.lines().next().unwrap_or("");
+    if line.chars().count() > 80 {
+        format!("{}…", line.chars().take(80).collect::<String>())
+    } else {
+        line.to_string()
+    }
+}