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/redis_cache.go

@@ -82,7 +82,6 @@ func (c *RedisCache) Delete(key string) {
 // DeleteByPrefix 根据前缀删除缓存
 func (c *RedisCache) DeleteByPrefix(prefix string) {
 	prefix = normalizePrefix(prefix)
-	// 使用原生客户端执行SCAN命令
 	rdb := c.client.GetClient()
 	var cursor uint64
 	for {
@@ -112,6 +111,30 @@ func (c *RedisCache) DeleteByPrefix(prefix string) {
 	}
 }
 
+// DeleteBatch 批量删除多个 key（使用 Redis Pipeline 减少网络往返）
+func (c *RedisCache) DeleteBatch(keys []string) {
+	if len(keys) == 0 {
+		return
+	}
+	normalizedKeys := make([]string, len(keys))
+	for i, k := range keys {
+		normalizedKeys[i] = normalizeKey(k)
+	}
+
+	recordInvalidateMultiple(int64(len(normalizedKeys)))
+	// 使用 pipeline 批量删除
+	pipe := c.client.GetClient().Pipeline()
+	for _, k := range normalizedKeys {
+		pipe.Del(c.ctx, k)
+	}
+	if _, err := pipe.Exec(c.ctx); err != nil {
+		zap.L().Error("Failed to batch delete keys",
+			zap.Int("count", len(normalizedKeys)),
+			zap.Error(err),
+		)
+	}
+}
+
 // Clear 清空所有缓存
 func (c *RedisCache) Clear() {
 	if settings.DisableFlushDB {