feat(call): integrate LiveKit for voice and video calling

Replace the manual WebRTC signaling implementation with LiveKit SFU. This includes:
- Adding LiveKit service, handler, and configuration.
- Updating Docker Compose to include LiveKit server, Redis, and PostgreSQL.
- Refactoring `CallService` and `WSHandler` to support LiveKit room readiness instead of raw SDP/ICE relaying.
- Adding new API endpoints for LiveKit token generation and webhooks.
- Removing deprecated WebRTC configuration and manual signaling DTOs.

internal/dto/call_dto.go

@@ -1,145 +0,0 @@
-package dto
-
-import (
-	"time"
-
-	"with_you/internal/model"
-)
-
-// ==================== Call Request DTOs ====================
-
-// StartCallRequest 发起通话请求
-type StartCallRequest struct {
-	ConversationID string         `json:"conversation_id" binding:"required"` // 会话ID
-	CallType       model.CallType `json:"call_type" binding:"required"`       // 通话类型: private, group
-}
-
-// AnswerCallRequest 接听通话请求
-type AnswerCallRequest struct {
-	SDP string `json:"sdp" binding:"required"` // SDP Answer
-}
-
-// SendSDPRequest 发送SDP请求
-type SendSDPRequest struct {
-	SDP  string `json:"sdp" binding:"required"`  // SDP Offer/Answer
-	Type string `json:"type" binding:"required"` // offer 或 answer
-}
-
-// SendICECandidateRequest 发送ICE候选请求
-type SendICECandidateRequest struct {
-	Candidate     string `json:"candidate" binding:"required"`      // candidate 字符串
-	SDPMid        string `json:"sdp_mid"`                           // SDP mid
-	SDPMLineIndex int16  `json:"sdp_mline_index"`                   // SDP m-line index
-}
-
-// ==================== Call Response DTOs ====================
-
-// CallSessionResponse 通话会话响应
-type CallSessionResponse struct {
-	ID             string                  `json:"id"`              // 通话ID
-	ConversationID string                  `json:"conversation_id"` // 会话ID
-	GroupID        string                  `json:"group_id,omitempty"`
-	CallerID       string                  `json:"caller_id"`       // 发起者ID
-	CallType       model.CallType          `json:"call_type"`       // 通话类型
-	Status         model.CallStatus        `json:"status"`          // 通话状态
-	StartedAt      *time.Time              `json:"started_at,omitempty"`
-	EndedAt        *time.Time              `json:"ended_at,omitempty"`
-	Duration       int64                   `json:"duration"`        // 通话时长(秒)
-	CreatedAt      time.Time               `json:"created_at"`
-	Participants   []CallParticipantResponse `json:"participants"`  // 参与者列表
-	Caller         *UserResponse           `json:"caller,omitempty"` // 发起者信息
-}
-
-// CallParticipantResponse 通话参与者响应
-type CallParticipantResponse struct {
-	UserID   string                 `json:"user_id"`
-	Status   model.ParticipantStatus `json:"status"`
-	JoinedAt *time.Time             `json:"joined_at,omitempty"`
-	LeftAt   *time.Time             `json:"left_at,omitempty"`
-	User     *UserResponse          `json:"user,omitempty"`
-}
-
-// ==================== Call SSE Event DTOs ====================
-
-// CallInviteEvent 来电邀请事件
-type CallInviteEvent struct {
-	CallID       string         `json:"call_id"`
-	ConversationID string       `json:"conversation_id"`
-	GroupID       string        `json:"group_id,omitempty"`
-	CallerID      string        `json:"caller_id"`
-	CallType      model.CallType `json:"call_type"`
-	Caller        *UserResponse `json:"caller,omitempty"`
-	CreatedAt     time.Time     `json:"created_at"`
-}
-
-// CallAnswerEvent 接听响应事件
-type CallAnswerEvent struct {
-	CallID    string `json:"call_id"`
-	UserID    string `json:"user_id"`
-	SDP       string `json:"sdp"`       // SDP Answer
-}
-
-// CallRejectEvent 拒绝通话事件
-type CallRejectEvent struct {
-	CallID string `json:"call_id"`
-	UserID string `json:"user_id"`
-}
-
-// CallEndEvent 结束通话事件
-type CallEndEvent struct {
-	CallID   string `json:"call_id"`
-	UserID   string `json:"user_id"`
-	Duration int64  `json:"duration"`
-}
-
-// CallICECandidateEvent ICE候选事件
-type CallICECandidateEvent struct {
-	CallID        string `json:"call_id"`
-	UserID        string `json:"user_id"`
-	Candidate     string `json:"candidate"`
-	SDPMid        string `json:"sdp_mid"`
-	SDPMLineIndex int16  `json:"sdp_mline_index"`
-}
-
-// CallSDPOfferEvent SDP Offer事件
-type CallSDPOfferEvent struct {
-	CallID string `json:"call_id"`
-	UserID string `json:"user_id"`
-	SDP    string `json:"sdp"`
-}
-
-// CallSDPAnswerEvent SDP Answer事件
-type CallSDPAnswerEvent struct {
-	CallID string `json:"call_id"`
-	UserID string `json:"user_id"`
-	SDP    string `json:"sdp"`
-}
-
-// CallUserJoinedEvent 用户加入通话事件(群聊)
-type CallUserJoinedEvent struct {
-	CallID string        `json:"call_id"`
-	UserID string        `json:"user_id"`
-	User   *UserResponse `json:"user,omitempty"`
-}
-
-// CallUserLeftEvent 用户离开通话事件(群聊)
-type CallUserLeftEvent struct {
-	CallID string `json:"call_id"`
-	UserID string `json:"user_id"`
-}
-
-// ==================== ICE Server Config ====================
-
-// ICEServerConfig ICE服务器配置
-type ICEServerConfig struct {
-	URLs           []string `json:"urls"`
-	Username       string   `json:"username,omitempty"`
-	Credential     string   `json:"credential,omitempty"`
-	CredentialType string   `json:"credential_type,omitempty"`
-}
-
-// CallConfigResponse 通话配置响应
-type CallConfigResponse struct {
-	ICEServers []ICEServerConfig `json:"ice_servers"`
-}
-