Add TURN relay support for daemon mode

-turn-url and -turn-secret flags on the daemon; credentials generated
using coturn use-auth-secret HMAC-SHA1 scheme (same as browser mode).
ICEServers field on mesh.Mesh threads extra ICE servers through to
every PeerConnection created by the anchor client.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

cmd/daemon/main.go

@@ -22,6 +22,8 @@ func main() {
 	anchorURL      := flag.String("anchor", "", "anchor WebSocket URL, e.g. ws://your-vps:17339/ws")
 	shareDir       := flag.String("share-dir", "", "directory to share with peers on the network")
 	joinInvite     := flag.String("join", "", "waste: invite string — sets anchor URL and auto-joins the network on startup")
+	turnURL        := flag.String("turn-url", "", "TURN server URL, e.g. turn:your-vps:3478")
+	turnSecret     := flag.String("turn-secret", "", "shared secret for coturn use-auth-secret HMAC credential")
 	importBackup   := flag.String("import-identity", "", "path to a yaw-key-backup-1 JSON file to import")
 	importPassword := flag.String("import-passphrase", "", "passphrase for --import-identity")
 	flag.Parse()
@@ -74,6 +76,8 @@ func main() {
 		StoreDir:       dir,
 		AnchorURL:      *anchorURL,
 		ShareDir:       expandHome(*shareDir),
+		TurnURL:        *turnURL,
+		TurnSecret:     *turnSecret,
 	})
 
 	if autoJoinNetwork != "" {