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/trade_dto.go

@@ -34,26 +34,6 @@ type TradeItemResponse struct {
 	UpdatedAt       string                `json:"updated_at"`
 }
 
-type TradeItemDetailResponse struct {
-	ID              string                `json:"id"`
-	UserID          string                `json:"user_id"`
-	TradeType       string                `json:"trade_type"`
-	Category        string                `json:"category"`
-	Title           string                `json:"title"`
-	Content         string                `json:"content"`
-	Segments        model.MessageSegments `json:"segments,omitempty"`
-	Images          []TradeImageResponse   `json:"images"`
-	Price           *float64              `json:"price,omitempty"`
-	Condition       string                `json:"condition,omitempty"`
-	Status          string                `json:"status"`
-	ViewsCount      int                   `json:"views_count"`
-	FavoritesCount  int                   `json:"favorites_count"`
-	IsFavorited     bool                  `json:"is_favorited"`
-	Author          *UserResponse         `json:"author"`
-	CreatedAt       string                `json:"created_at"`
-	UpdatedAt       string                `json:"updated_at"`
-}
-
 type CreateTradeItemRequest struct {
 	TradeType     string                `json:"trade_type" binding:"required,oneof=sell buy"`
 	Category      string                `json:"category" binding:"required,oneof=digital book clothing daily cosmetics sport ticket other"`