feat(webrtc): add standalone webrtc-poc binary for M1 testing

Minimal egress-only server that wires Source, Registry, PeerFactory and
WHEPHandler together on a single stream id. Listens for RTP on a local
UDP port (default 127.0.0.1:10000) and serves WHEP on :8787.

Not part of the Core binary — will be demoted to an internal test helper
once M2 integrates WebRTC output into the process-graph.

cmd/webrtc-poc/main.go

@@ -0,0 +1,55 @@
+// Command webrtc-poc runs a minimal Dragon Fork WebRTC egress server for
+// manual end-to-end testing. It listens for RTP on 127.0.0.1:10000 as
+// stream "test" and serves WHEP at :8787.
+//
+// This is NOT part of the datarhei Core binary. It will be removed or
+// demoted to an internal test helper once milestone M2 lands.
+package main
+
+import (
+	"flag"
+	"log"
+	"net/http"
+
+	"github.com/datarhei/core/v16/core/webrtc"
+)
+
+func main() {
+	var (
+		streamID = flag.String("stream", "test", "stream id to serve")
+		rtpPort  = flag.Int("rtp-port", 10000, "UDP port to receive RTP on")
+		listen   = flag.String("listen", ":8787", "WHEP HTTP listen address")
+		publicIP = flag.String("public-ip", "", "server public IP for NAT1To1 (optional)")
+	)
+	flag.Parse()
+
+	cfg := webrtc.DefaultConfig()
+	cfg.WHEPListen = *listen
+	cfg.PublicIP = *publicIP
+
+	src, err := webrtc.NewSource(*streamID, *rtpPort)
+	if err != nil {
+		log.Fatalf("NewSource: %v", err)
+	}
+	src.Start()
+	defer src.Close()
+	log.Printf("listening for RTP on %s", src.LocalAddr())
+
+	reg := webrtc.NewRegistry()
+	if err := reg.Register(*streamID, src); err != nil {
+		log.Fatalf("Register: %v", err)
+	}
+
+	factory, err := webrtc.NewPeerFactory(cfg)
+	if err != nil {
+		log.Fatalf("NewPeerFactory: %v", err)
+	}
+
+	handler := webrtc.NewWHEPHandler(reg, factory, cfg)
+
+	mux := http.NewServeMux()
+	mux.Handle("/whep/", handler)
+
+	log.Printf("WHEP listening on %s — POST /whep/%s to subscribe", *listen, *streamID)
+	log.Fatal(http.ListenAndServe(*listen, mux))
+}