botserv: op assigned bots on join; statserv: persist counters across restart

Problem 1: an assigned bot joined via IJOIN with no status mode, so it had no
+o. Join it with the 4-param IJOIN form (ts 1, mode o) so it's opped, matching
Anope's default bot modes (+o), and exempt bots from SECUREOPS/RESTRICTED so the
op is never stripped.

Problem 2: the shared stat counters lived only in memory, so a restart wiped
them. Snapshot them to the log (StatsSet event, folded into NetData + compaction)
periodically and on shutdown, and reseed the live registry from the log at
startup. Live gauges (online counts) stay re-derived, not stored.

src/grpc.rs

@@ -181,6 +181,7 @@ fn to_wire(entry: &LogEntry) -> Option<ReplicationEvent> {
         | Event::ForbidRemoved { .. }
         | Event::JupeAdded { .. }
         | Event::JupeRemoved { .. }
+        | Event::StatsSet { .. }
         | Event::AccountExpiryWarned { .. }
         | Event::ChannelExpiryWarned { .. }
         | Event::AccountOperNoteSet { .. }