Phase 2 backend: LiveKit voice integration

Backend:
- internal/voice/client.go: LiveKit token generation, room management, participant listing
- internal/voice/handlers.go: POST /voice/token, GET /voice/rooms/{roomID}/participants
- internal/gateway/events.go: added VOICE_JOIN, VOICE_LEAVE, VOICE_MUTE, VOICE_DEAFEN events
- cmd/server/main.go: wired voice client and routes under /api/v1/voice
- Docker: livekit.yaml config verified

Frontend deps:
- Added livekit-client and @livekit/components-react packages

internal/voice/client.go

@@ -0,0 +1,104 @@
+package voice
+
+import (
+	"context"
+	"fmt"
+	"time"
+
+	lksdk "github.com/livekit/server-sdk-go/v2"
+	"github.com/livekit/protocol/auth"
+	"github.com/livekit/protocol/livekit"
+)
+
+type Client struct {
+	apiKey    string
+	apiSecret string
+	url       string
+	roomClient *lksdk.RoomServiceClient
+}
+
+func NewClient(apiKey, apiSecret, url string) *Client {
+	if apiKey == "" || apiSecret == "" {
+		return nil
+	}
+
+	roomClient := lksdk.NewRoomServiceClient(url, apiKey, apiSecret)
+
+	return &Client{
+		apiKey:     apiKey,
+		apiSecret:  apiSecret,
+		url:        url,
+		roomClient: roomClient,
+	}
+}
+
+func (c *Client) GenerateToken(roomName, participantID, identity string) (string, error) {
+	if c == nil {
+		return "", fmt.Errorf("voice client not configured")
+	}
+
+	at := auth.NewAccessToken(c.apiKey, c.apiSecret)
+	grant := &auth.VideoGrant{
+		RoomJoin:     true,
+		Room:         roomName,
+		CanPublish:   boolPtr(true),
+		CanSubscribe: boolPtr(true),
+	}
+	at.SetVideoGrant(grant)
+	at.SetIdentity(identity)
+	at.SetValidFor(time.Hour)
+
+	token, err := at.ToJWT()
+	if err != nil {
+		return "", fmt.Errorf("generate token: %w", err)
+	}
+
+	return token, nil
+}
+
+func (c *Client) CreateRoom(name string) (*livekit.Room, error) {
+	if c == nil {
+		return nil, fmt.Errorf("voice client not configured")
+	}
+
+	room, err := c.roomClient.CreateRoom(context.Background(), &livekit.CreateRoomRequest{
+		Name: name,
+		EmptyTimeout: 300, // 5 minutes before auto-delete when empty
+		MaxParticipants: 20,
+	})
+	if err != nil {
+		return nil, fmt.Errorf("create room: %w", err)
+	}
+
+	return room, nil
+}
+
+func (c *Client) DeleteRoom(name string) error {
+	if c == nil {
+		return fmt.Errorf("voice client not configured")
+	}
+
+	_, err := c.roomClient.DeleteRoom(context.Background(), &livekit.DeleteRoomRequest{
+		Room: name,
+	})
+	return err
+}
+
+func (c *Client) ListParticipants(roomName string) ([]*livekit.ParticipantInfo, error) {
+	if c == nil {
+		return nil, fmt.Errorf("voice client not configured")
+	}
+
+	resp, err := c.roomClient.ListParticipants(context.Background(), &livekit.ListParticipantsRequest{
+		Room: roomName,
+	})
+	if err != nil {
+		return nil, fmt.Errorf("list participants: %w", err)
+	}
+
+	return resp.Participants, nil
+}
+
+func boolPtr(b bool) *bool {
+	return &b
+}