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/cache/keys.go

@@ -35,11 +35,12 @@ const (
 	PrefixChannelsAllList = "channels:all_list"
 
 	// 消息缓存相关
-	keyPrefixMsgHash  = "msg_hash"  // 消息详情 Hash
-	keyPrefixMsgIndex = "msg_index" // 消息索引 Sorted Set
-	keyPrefixMsgCount = "msg_count" // 消息计数
-	keyPrefixMsgSeq   = "msg_seq"   // Seq 计数器
-	keyPrefixMsgPage  = "msg_page"  // 分页缓存
+	keyPrefixMsgHash     = "msg_hash"   // 消息详情 Hash
+	keyPrefixMsgIndex    = "msg_index"  // 消息索引 Sorted Set
+	keyPrefixMsgCount    = "msg_count"  // 消息计数
+	keyPrefixMsgSeq      = "msg_seq"    // Seq 计数器
+	keyPrefixMsgPage     = "msg_page"   // 分页缓存
+	keyPrefixMsgIdempotent = "msg_idem"  // 消息幂等键
 )
 
 // PostListKey 生成帖子列表缓存键
@@ -221,3 +222,13 @@ func MessagePageKey(convID string, page, pageSize int) string {
 func InvalidateMessagePages(cache Cache, conversationID string) {
 	cache.DeleteByPrefix(fmt.Sprintf("%s:%s:", keyPrefixMsgPage, conversationID))
 }
+
+// MessageIdempotentKey 消息幂等键 (clientMsgID -> server MsgID)
+func MessageIdempotentKey(senderID, clientMsgID string) string {
+	return fmt.Sprintf("%s:%s:%s", keyPrefixMsgIdempotent, senderID, clientMsgID)
+}
+
+// PushDedupKey 推送去重键，防止同一消息重复推送给同一用户
+func PushDedupKey(userID, messageID string) string {
+	return fmt.Sprintf("push_dedup:%s:%s", userID, messageID)
+}