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/repository/group_repo.go

@@ -21,6 +21,7 @@ type GroupRepository interface {
 
 	// 群成员操作
 	AddMember(member *model.GroupMember) error
+	BatchAddMembers(groupID string, members []*model.GroupMember) error
 	GetMember(groupID string, userID string) (*model.GroupMember, error)
 	GetMembers(groupID string, page, pageSize int) ([]model.GroupMember, int64, error)
 	UpdateMember(member *model.GroupMember) error
@@ -53,6 +54,9 @@ type GroupRepository interface {
 	GetUserGroupsByCursor(ctx context.Context, userID string, req *cursor.PageRequest) (*cursor.CursorPageResult[*model.Group], error)
 	GetMembersByCursor(ctx context.Context, groupID string, req *cursor.PageRequest) (*cursor.CursorPageResult[*model.GroupMember], error)
 	GetAnnouncementsByCursor(ctx context.Context, groupID string, req *cursor.PageRequest) (*cursor.CursorPageResult[*model.GroupAnnouncement], error)
+
+	// 批量操作
+	GetExistingMembers(groupID string, userIDs []string) (map[string]bool, error)
 }
 
 // GroupMemberWithUser 群成员带用户信息的结构
@@ -155,12 +159,24 @@ func (r *groupRepository) AddMember(member *model.GroupMember) error {
 		if err := tx.Create(member).Error; err != nil {
 			return err
 		}
-		// 更新群组成员数量
 		return tx.Model(&model.Group{}).Where("id = ?", member.GroupID).
 			Update("member_count", gorm.Expr("member_count + ?", 1)).Error
 	})
 }
 
+func (r *groupRepository) BatchAddMembers(groupID string, members []*model.GroupMember) error {
+	if len(members) == 0 {
+		return nil
+	}
+	return r.db.Transaction(func(tx *gorm.DB) error {
+		if err := tx.CreateInBatches(members, 100).Error; err != nil {
+			return err
+		}
+		return tx.Model(&model.Group{}).Where("id = ?", groupID).
+			Update("member_count", gorm.Expr("member_count + ?", len(members))).Error
+	})
+}
+
 // GetMember 获取群成员
 func (r *groupRepository) GetMember(groupID string, userID string) (*model.GroupMember, error) {
 	var member model.GroupMember