refactor: improve system stability, performance, and code structure

This commit introduces several architectural improvements and optimizations across the codebase:

- **Performance & Reliability**:
  - Implemented Redis pipelining in `ConversationCache.CacheMessage` to reduce network round-trips.
  - Added a circuit breaker to the JPush client to prevent cascading failures.
  - Introduced batch deletion and batch member addition capabilities in repositories.
  - Added message idempotency support using `client_msg_id` and a Redis-based cache.
  - Optimized WebSocket handling with connection limits (total and per-user) and improved error logging.

- **Code Refactoring**:
  - Refactored `Router` to use a `RouterDeps` struct, simplifying the constructor and improving maintainability.
  - Unified model ID generation logic using new `id_helper.go` (supporting UUID and Snowflake).
  - Standardized JSON serialization/deserialization in models using `json_helper.go`.
  - Refactored DTO conversion logic, specifically for `UserResponse` (using functional options) and `Report` responses.
  - Removed redundant/deprecated DTOs like `PostDetailResponse` and `TradeItemDetailResponse`.

- **Cache Improvements**:
  - Enhanced `LayeredCache` with `SetRaw` to avoid double-encoding when promoting values from Redis to local cache.
  - Added `DeleteBatch` support to the cache interface.

- **Other Changes**:
  - Cleaned up `config.go` by removing redundant default values and explicit environment variable overrides.
  - Improved WebSocket registration flow to handle connection limits gracefully.

internal/dto/dto.go

@@ -177,33 +177,6 @@ type PostResponse struct {
 	Channel         *PostChannelBrief     `json:"channel,omitempty"`
 }
 
-// PostDetailResponse 帖子详情响应
-type PostDetailResponse struct {
-	ID              string                `json:"id"`
-	UserID          string                `json:"user_id"`
-	ChannelID       *string               `json:"channel_id,omitempty"`
-	Title           string                `json:"title"`
-	Content         string                `json:"content"`
-	Segments        model.MessageSegments `json:"segments,omitempty"`
-	Images          []PostImageResponse   `json:"images"`
-	Status          string                `json:"status"`
-	LikesCount      int                   `json:"likes_count"`
-	CommentsCount   int                   `json:"comments_count"`
-	FavoritesCount  int                   `json:"favorites_count"`
-	SharesCount     int                   `json:"shares_count"`
-	ViewsCount      int                   `json:"views_count"`
-	IsPinned        bool                  `json:"is_pinned"`
-	IsLocked        bool                  `json:"is_locked"`
-	IsVote          bool                  `json:"is_vote"`
-	CreatedAt       string                `json:"created_at"`
-	UpdatedAt       string                `json:"updated_at"`
-	ContentEditedAt string                `json:"content_edited_at,omitempty"`
-	Author          *UserResponse         `json:"author"`
-	IsLiked         bool                  `json:"is_liked"`
-	IsFavorited     bool                  `json:"is_favorited"`
-	Channel         *PostChannelBrief     `json:"channel,omitempty"`
-}
-
 // ==================== Comment DTOs ====================
 
 // CommentImageResponse 评论图片响应
@@ -454,8 +427,9 @@ type CreateConversationRequest struct {
 
 // SendMessageRequest 发送消息请求
 type SendMessageRequest struct {
-	Segments  model.MessageSegments `json:"segments" binding:"required"` // 消息链（必须）
-	ReplyToID *string               `json:"reply_to_id,omitempty"`       // 回复的消息ID (string类型)
+	Segments    model.MessageSegments `json:"segments" binding:"required"` // 消息链（必须）
+	ReplyToID   *string               `json:"reply_to_id,omitempty"`         // 回复的消息ID (string类型)
+	ClientMsgID string                `json:"client_msg_id,omitempty"`      // 客户端消息ID（幂等性去重）
 }
 
 // MarkReadRequest 标记已读请求
@@ -751,10 +725,11 @@ type WSEventResponse struct {
 
 // SendMessageParams 发送消息参数（用于 REST API）
 type SendMessageParams struct {
-	DetailType     string                `json:"detail_type"`           // 消息类型: private, group
-	ConversationID string                `json:"conversation_id"`       // 会话ID
-	Segments       model.MessageSegments `json:"segments"`              // 消息内容（消息段数组）
-	ReplyToID      *string               `json:"reply_to_id,omitempty"` // 回复的消息ID
+	DetailType     string                `json:"detail_type"`                // 消息类型: private, group
+	ConversationID string                `json:"conversation_id"`            // 会话ID
+	Segments       model.MessageSegments `json:"segments"`                   // 消息内容（消息段数组）
+	ReplyToID      *string               `json:"reply_to_id,omitempty"`      // 回复的消息ID
+	ClientMsgID    string                `json:"client_msg_id,omitempty"`    // 客户端消息ID（幂等性去重）
 }
 
 // DeleteMsgParams 撤回消息参数