⭐ 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/shared/participant.go

@@ -0,0 +1,44 @@
+package shared
+
+import (
+	"fmt"
+	"relay/internal/common"
+	"relay/internal/connections"
+
+	"github.com/oklog/ulid/v2"
+	"github.com/pion/webrtc/v4"
+)
+
+type Participant struct {
+	ID             ulid.ULID
+	PeerConnection *webrtc.PeerConnection
+	DataChannel    *connections.NestriDataChannel
+}
+
+func NewParticipant() (*Participant, error) {
+	id, err := common.NewULID()
+	if err != nil {
+		return nil, fmt.Errorf("failed to create ULID for Participant: %w", err)
+	}
+	return &Participant{
+		ID: id,
+	}, nil
+}
+
+func (p *Participant) addTrack(trackLocal *webrtc.TrackLocalStaticRTP) error {
+	rtpSender, err := p.PeerConnection.AddTrack(trackLocal)
+	if err != nil {
+		return err
+	}
+
+	go func() {
+		rtcpBuffer := make([]byte, 1400)
+		for {
+			if _, _, rtcpErr := rtpSender.Read(rtcpBuffer); rtcpErr != nil {
+				break
+			}
+		}
+	}()
+
+	return nil
+}