modules: split services and the ircd link into external crates

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.

chanserv/src/getkey.rs

@@ -0,0 +1,19 @@
+use fedserv_api::Store;
+use fedserv_api::{Sender, ServiceCtx};
+use fedserv_api::NetView;
+
+// GETKEY <#channel>: report the channel key (+k), for ops who need to let
+// someone in.
+pub fn handle(me: &str, from: &Sender, args: &[&str], ctx: &mut ServiceCtx, net: &dyn NetView, db: &dyn Store) {
+    let Some(&chan) = args.get(1) else {
+        ctx.notice(me, from.uid, "Syntax: GETKEY <#channel>");
+        return;
+    };
+    if !super::require_op(me, from, chan, ctx, db) {
+        return;
+    }
+    match net.channel_key(chan) {
+        Some(key) => ctx.notice(me, from.uid, format!("Key for \x02{chan}\x02 is \x02{key}\x02.")),
+        None => ctx.notice(me, from.uid, format!("\x02{chan}\x02 has no key set.")),
+    }
+}