Introduce a typed ChanSettings struct + ChanSetting enum for ChanServ's on/off
options instead of a bag of string flags, so a new option is one field and the
compiler proves every site handles it. First two, both functional: SIGNKICK
attributes ChanServ kicks with who requested them; PRIVATE hides the channel
from LIST. Folded through the event log like the other channel state (node-local,
no gossip), shown in INFO. One ChannelSettingsSet event, one Store method.
nickserv, chanserv and the InspIRCd protocol move out of the binary into their
own workspace crates (fedserv-nickserv, fedserv-chanserv, fedserv-inspircd),
each depending only on fedserv-api. human_time and the branded account emails
move into the SDK crate so a module needs nothing from core; the engine keeps
its own inherent methods and builds emails via fedserv-api too. The bin now
constructs each module from its crate instead of an in-tree #[path] include.
Proves the SDK is self-sufficient: a third-party module is the same shape.
