feat: optimize connection pooling and improve Kiro executor reliability

## 中文说明

### 连接池优化
- 为 AMP 代理、SOCKS5 代理和 HTTP 代理配置优化的连接池参数
- MaxIdleConnsPerHost 从默认的 2 增加到 20，支持更多并发用户
- MaxConnsPerHost 设为 0（无限制），避免连接瓶颈
- 添加 IdleConnTimeout (90s) 和其他超时配置

### Kiro 执行器增强
- 添加 Event Stream 消息解析的边界保护，防止越界访问
- 实现实时使用量估算（每 5000 字符或 15 秒发送 ping 事件）
- 正确从上游事件中提取并传递 stop_reason
- 改进输入 token 计算，优先使用 Claude 格式解析
- 添加 max_tokens 截断警告日志

### Token 计算改进
- 添加 tokenizer 缓存（sync.Map）避免重复创建
- 为 Claude/Kiro/AmazonQ 模型添加 1.1 调整因子
- 新增 countClaudeChatTokens 函数支持 Claude API 格式
- 支持图像 token 估算（基于尺寸计算）

### 认证刷新优化
- RefreshLead 从 30 分钟改为 5 分钟，与 Antigravity 保持一致
- 修复 NextRefreshAfter 设置，防止频繁刷新检查
- refreshFailureBackoff 从 5 分钟改为 1 分钟，加快失败恢复

---

## English Description

### Connection Pool Optimization
- Configure optimized connection pool parameters for AMP proxy, SOCKS5 proxy, and HTTP proxy
- Increase MaxIdleConnsPerHost from default 2 to 20 to support more concurrent users
- Set MaxConnsPerHost to 0 (unlimited) to avoid connection bottlenecks
- Add IdleConnTimeout (90s) and other timeout configurations

### Kiro Executor Enhancements
- Add boundary protection for Event Stream message parsing to prevent out-of-bounds access
- Implement real-time usage estimation (send ping events every 5000 chars or 15 seconds)
- Correctly extract and pass stop_reason from upstream events
- Improve input token calculation, prioritize Claude format parsing
- Add max_tokens truncation warning logs

### Token Calculation Improvements
- Add tokenizer cache (sync.Map) to avoid repeated creation
- Add 1.1 adjustment factor for Claude/Kiro/AmazonQ models
- Add countClaudeChatTokens function to support Claude API format
- Support image token estimation (calculated based on dimensions)

### Authentication Refresh Optimization
- Change RefreshLead from 30 minutes to 5 minutes, consistent with Antigravity
- Fix NextRefreshAfter setting to prevent frequent refresh checks
- Change refreshFailureBackoff from 5 minutes to 1 minute for faster failure recovery

internal/util/proxy.go

@@ -8,6 +8,7 @@ import (
 	"net"
 	"net/http"
 	"net/url"
+	"time"
 
 	"github.com/router-for-me/CLIProxyAPI/v6/sdk/config"
 	log "github.com/sirupsen/logrus"
@@ -36,15 +37,25 @@ func SetProxy(cfg *config.SDKConfig, httpClient *http.Client) *http.Client {
 				log.Errorf("create SOCKS5 dialer failed: %v", errSOCKS5)
 				return httpClient
 			}
-			// Set up a custom transport using the SOCKS5 dialer.
+			// Set up a custom transport using the SOCKS5 dialer with optimized connection pooling
 			transport = &http.Transport{
 				DialContext: func(ctx context.Context, network, addr string) (net.Conn, error) {
 					return dialer.Dial(network, addr)
 				},
+				MaxIdleConns:        100,
+				MaxIdleConnsPerHost: 20, // Increased from default 2 to support more concurrent users
+				MaxConnsPerHost:     0, // No limit on max concurrent connections per host
+				IdleConnTimeout:     90 * time.Second,
 			}
 		} else if proxyURL.Scheme == "http" || proxyURL.Scheme == "https" {
-			// Configure HTTP or HTTPS proxy.
-			transport = &http.Transport{Proxy: http.ProxyURL(proxyURL)}
+			// Configure HTTP or HTTPS proxy with optimized connection pooling
+			transport = &http.Transport{
+				Proxy:               http.ProxyURL(proxyURL),
+				MaxIdleConns:        100,
+				MaxIdleConnsPerHost: 20, // Increased from default 2 to support more concurrent users
+				MaxConnsPerHost:     0, // No limit on max concurrent connections per host
+				IdleConnTimeout:     90 * time.Second,
+			}
 		}
 	}
 	// If a new transport was created, apply it to the HTTP client.