guestlink v1: self-hosted guest line (Cleanfeed replacement)

Go + Pion + libopus. One guest, live audio both ways, anonymous chat.
README for this version was not preserved; see the next commit.

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

.gitignore

@@ -0,0 +1,5 @@
+/guestlink
+/guestlink.new
+/glprobe
+/backup-*/
+*.raw