memoserv: complete + improve the memo service

Finish MemoServ on the typed, event-logged memo model: Db memo_send/list/read/
del/unread_memos + Store facade, and a new fedserv-memoserv crate (a default
service). Beyond the basics: SEND caps a mailbox (30) so nobody's flooded, READ
takes <num>|NEW|ALL, DEL takes <num>|ALL, LIST previews and flags unread, and
NickServ notifies you of waiting memos on login. Memos persist and federate
(Global scope) like other account data. Also lands NetAction::QuitUser (BotServ
plumbing). Data + delivery/login-notify tests.

src/grpc.rs

@@ -126,6 +126,9 @@ fn to_wire(entry: &LogEntry) -> Option<ReplicationEvent> {
         | Event::AjoinRemoved { .. }
         | Event::AccountSuspended { .. }
         | Event::AccountUnsuspended { .. }
+        | Event::MemoSent { .. }
+        | Event::MemoRead { .. }
+        | Event::MemoDeleted { .. }
         | Event::ChannelMlock { .. }
         | Event::ChannelAccessAdd { .. }
         | Event::ChannelAccessDel { .. }
@@ -363,6 +366,7 @@ mod tests {
             verified: true,
             ajoin: vec![],
             suspension: None,
+            memos: vec![],
         };
         let registered = LogEntry::for_test("A", 0, 1, Event::AccountRegistered(acct));
         let wire = to_wire(&registered).expect("account registration replicates");