Services no longer receive the concrete account store. on_command now takes
&mut dyn Store + &dyn NetView (both defined in fedserv-api); the engine's Db
and Network implement them. Reads hand back plain views (AccountView,
ChannelView, ...) carrying only non-secret fields, so the event log, gossip,
and credential material (password hash, SCRAM verifiers) are unreachable from
a module. All command modules ported; behaviour unchanged.
Adds channel moderation commands sourced from the ChanServ pseudoclient.
Tracks connected users' nicks and hosts so targets can be resolved by
nick and banned by *!*@host. All commands require operator access.
