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.
ACCESS <#channel> LIST|ADD|DEL manages op/voice by account (founder-only
changes). Entries are ChannelAccessAdd/Del events, so they replicate and
compact like the rest, and join grants +o/+v from the list.
