⭐ feat: Migrate from WebSocket to libp2p for peer-to-peer connectivity (#286)

## Description
Whew, some stuff is still not re-implemented, but it's working!

Rabbit's gonna explode with the amount of changes I reckon 😅



<!-- This is an auto-generated comment: release notes by coderabbit.ai
-->
## Summary by CodeRabbit

- **New Features**
- Introduced a peer-to-peer relay system using libp2p with enhanced
stream forwarding, room state synchronization, and mDNS peer discovery.
- Added decentralized room and participant management, metrics
publishing, and safe, size-limited, concurrent message streaming with
robust framing and callback dispatching.
- Implemented asynchronous, callback-driven message handling over custom
libp2p streams replacing WebSocket signaling.
- **Improvements**
- Migrated signaling and stream protocols from WebSocket to libp2p,
improving reliability and scalability.
- Simplified configuration and environment variables, removing
deprecated flags and adding persistent data support.
- Enhanced logging, error handling, and connection management for better
observability and robustness.
- Refined RTP header extension registration and NAT IP handling for
improved WebRTC performance.
- **Bug Fixes**
- Improved ICE candidate buffering and SDP negotiation in WebRTC
connections.
  - Fixed NAT IP and UDP port range configuration issues.
- **Refactor**
- Modularized codebase, reorganized relay and server logic, and removed
deprecated WebSocket-based components.
- Streamlined message structures, removed obsolete enums and message
types, and simplified SafeMap concurrency.
- Replaced WebSocket signaling with libp2p stream protocols in server
and relay components.
- **Chores**
- Updated and cleaned dependencies across Go, Rust, and JavaScript
packages.
  - Added `.gitignore` for persistent data directory in relay package.
<!-- end of auto-generated comment: release notes by coderabbit.ai -->

---------

Co-authored-by: DatCaptainHorse <DatCaptainHorse@users.noreply.github.com>
Co-authored-by: Philipp Neumann <3daquawolf@gmail.com>

packages/relay/internal/common/common.go

@@ -2,12 +2,13 @@ package common
 
 import (
 	"fmt"
+	"log/slog"
+	"strconv"
+
 	"github.com/libp2p/go-reuseport"
 	"github.com/pion/ice/v4"
 	"github.com/pion/interceptor"
 	"github.com/pion/webrtc/v4"
-	"log/slog"
-	"strconv"
 )
 
 var globalWebRTCAPI *webrtc.API
@@ -24,17 +25,9 @@ func InitWebRTCAPI() error {
 	// Media engine
 	mediaEngine := &webrtc.MediaEngine{}
 
-	// Register additional header extensions to reduce latency
-	// Playout Delay
-	if err := mediaEngine.RegisterHeaderExtension(webrtc.RTPHeaderExtensionCapability{
-		URI: ExtensionPlayoutDelay,
-	}, webrtc.RTPCodecTypeVideo); err != nil {
-		return err
-	}
-	if err := mediaEngine.RegisterHeaderExtension(webrtc.RTPHeaderExtensionCapability{
-		URI: ExtensionPlayoutDelay,
-	}, webrtc.RTPCodecTypeAudio); err != nil {
-		return err
+	// Register our extensions
+	if err := RegisterExtensions(mediaEngine); err != nil {
+		return fmt.Errorf("failed to register extensions: %w", err)
 	}
 
 	// Default codecs cover most of our needs
@@ -75,9 +68,10 @@ func InitWebRTCAPI() error {
 	// New in v4, reduces CPU usage and latency when enabled
 	settingEngine.EnableSCTPZeroChecksum(true)
 
-	nat11IPs := GetFlags().NAT11IPs
-	if len(nat11IPs) > 0 {
-		settingEngine.SetNAT1To1IPs(nat11IPs, webrtc.ICECandidateTypeHost)
+	nat11IP := GetFlags().NAT11IP
+	if len(nat11IP) > 0 {
+		settingEngine.SetNAT1To1IPs([]string{nat11IP}, webrtc.ICECandidateTypeSrflx)
+		slog.Info("Using NAT 1:1 IP for WebRTC", "nat11_ip", nat11IP)
 	}
 
 	muxPort := GetFlags().UDPMuxPort
@@ -85,7 +79,7 @@ func InitWebRTCAPI() error {
 		// Use reuseport to allow multiple listeners on the same port
 		pktListener, err := reuseport.ListenPacket("udp", ":"+strconv.Itoa(muxPort))
 		if err != nil {
-			return fmt.Errorf("failed to create UDP listener: %w", err)
+			return fmt.Errorf("failed to create WebRTC muxed UDP listener: %w", err)
 		}
 
 		mux := ice.NewMultiUDPMuxDefault(ice.NewUDPMuxDefault(ice.UDPMuxParams{
@@ -95,10 +89,13 @@ func InitWebRTCAPI() error {
 		settingEngine.SetICEUDPMux(mux)
 	}
 
-	// Set the UDP port range used by WebRTC
-	err = settingEngine.SetEphemeralUDPPortRange(uint16(flags.WebRTCUDPStart), uint16(flags.WebRTCUDPEnd))
-	if err != nil {
-		return err
+	if flags.WebRTCUDPStart > 0 && flags.WebRTCUDPEnd > 0 && flags.WebRTCUDPStart < flags.WebRTCUDPEnd {
+		// Set the UDP port range used by WebRTC
+		err = settingEngine.SetEphemeralUDPPortRange(uint16(flags.WebRTCUDPStart), uint16(flags.WebRTCUDPEnd))
+		if err != nil {
+			return err
+		}
+		slog.Info("Using WebRTC UDP Port Range", "start", flags.WebRTCUDPStart, "end", flags.WebRTCUDPEnd)
 	}
 
 	settingEngine.SetIncludeLoopbackCandidate(true) // Just in case
@@ -109,11 +106,6 @@ func InitWebRTCAPI() error {
 	return nil
 }
 
-// GetWebRTCAPI returns the global WebRTC API
-func GetWebRTCAPI() *webrtc.API {
-	return globalWebRTCAPI
-}
-
 // CreatePeerConnection sets up a new peer connection
 func CreatePeerConnection(onClose func()) (*webrtc.PeerConnection, error) {
 	pc, err := globalWebRTCAPI.NewPeerConnection(globalWebRTCConfig)