Add the Bamboo site agent

The site agent: a WireGuard peer that dials out to each edge, accepts TCP
streams and native UDP datagrams inside the tunnel, lists local Docker
containers, and runs the local SMTP relay for mail egress. Split out of the
original single repository; depends on Reef for the shared types.

Co-Authored-By: Claude Sonnet 5.5 <noreply@anthropic.com>

.gitignore

@@ -0,0 +1,4 @@
+bin/
+*-data/
+.env
+wg.key