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/model/system_notification.go

@@ -2,13 +2,9 @@
 
 import (
 	"database/sql/driver"
-	"encoding/json"
-	"errors"
 	"time"
 
 	"gorm.io/gorm"
-
-	"with_you/internal/pkg/utils"
 )
 
 // SystemNotificationType 系统通知类型
@@ -71,24 +67,12 @@ type SystemNotificationExtra struct {
 
 // Value 实现driver.Valuer接口
 func (e SystemNotificationExtra) Value() (driver.Value, error) {
-	return json.Marshal(e)
+	return ValueJSON(e)
 }
 
 // Scan 实现sql.Scanner接口
 func (e *SystemNotificationExtra) Scan(value any) error {
-	if value == nil {
-		return nil
-	}
-	var data []byte
-	switch v := value.(type) {
-	case []byte:
-		data = v
-	case string:
-		data = []byte(v)
-	default:
-		return errors.New("type assertion to []byte or string failed")
-	}
-	return json.Unmarshal(data, e)
+	return ScanJSON(e, value)
 }
 
 // SystemNotification 系统通知（独立表，与消息完全分离）
@@ -113,14 +97,7 @@ type SystemNotification struct {
 
 // BeforeCreate 创建前生成雪花算法ID
 func (n *SystemNotification) BeforeCreate(tx *gorm.DB) error {
-	if n.ID == 0 {
-		id, err := utils.GetSnowflake().GenerateID()
-		if err != nil {
-			return err
-		}
-		n.ID = id
-	}
-	return nil
+	return SetSnowflakeInt64ID(&n.ID)
 }
 
 // TableName 指定表名