feat: v2.1.0 核心重构与功能增强

## 架构重构
- 全局变量消除，迁移至 Config/State 对象
- SMB 插件融合（smb/smb2/smbghost/smbinfo）
- 服务探测重构，实现 Nmap 风格 fallback 机制
- 输出系统重构，TXT 实时刷盘 + 双写机制
- i18n 框架升级至 go-i18n

## 性能优化
- 正则表达式预编译
- 内存优化 map[string]struct{}
- 并发指纹匹配
- SOCKS5 连接复用
- 滑动窗口调度 + 自适应线程池

## 新功能
- Web 管理界面
- 多格式 POC 适配（xray/afrog）
- 增强指纹库（3139条）
- Favicon hash 指纹识别
- 插件选择性编译（Build Tags）
- fscan-lab 靶场环境
- 默认端口扩展（62→133）

## 构建系统
- 添加 no_local tag 支持排除本地插件
- 多版本构建：fscan/fscan-nolocal/fscan-web
- CI 添加 snapshot 模式支持仅测试构建

## Bug 修复
- 修复 120+ 个问题，包括 RDP panic、批量扫描漏报、
  JSON 输出格式、Redis 检测、Context 超时等

## 测试增强
- 单元测试覆盖率 74-100%
- 并发安全测试
- 集成测试（Web/端口/服务/SSH/ICMP）

plugins/services/mysql.go

@@ -0,0 +1,211 @@
+//go:build plugin_mysql || !plugin_selective
+
+package services
+
+import (
+	"context"
+	"database/sql"
+	"fmt"
+	"log"
+	"net"
+	"time"
+
+	"github.com/go-sql-driver/mysql"
+	"github.com/shadow1ng/fscan/common"
+	"github.com/shadow1ng/fscan/common/i18n"
+	"github.com/shadow1ng/fscan/plugins"
+)
+
+type nullWriter struct{}
+
+func (nullWriter) Write(p []byte) (int, error) { return len(p), nil }
+
+func init() {
+	// 禁用mysql驱动的错误日志（如unexpected EOF）
+	_ = mysql.SetLogger(log.New(&nullWriter{}, "", 0))
+}
+
+// MySQLPlugin MySQL数据库扫描插件
+type MySQLPlugin struct {
+	plugins.BasePlugin
+}
+
+func NewMySQLPlugin() *MySQLPlugin {
+	return &MySQLPlugin{
+		BasePlugin: plugins.NewBasePlugin("mysql"),
+	}
+}
+
+func (p *MySQLPlugin) Scan(ctx context.Context, info *common.HostInfo, config *common.Config, state *common.State) *ScanResult {
+	if config.DisableBrute {
+		return p.identifyService(info, config)
+	}
+
+	credentials := GenerateCredentials("mysql", config)
+	if len(credentials) == 0 {
+		return &ScanResult{
+			Success: false,
+			Service: "mysql",
+			Error:   fmt.Errorf("没有可用的测试凭据"),
+		}
+	}
+
+	target := info.Target()
+
+	// 使用公共框架进行并发凭据测试
+	authFn := p.createAuthFunc(info, config, state)
+	testConfig := DefaultConcurrentTestConfig(config)
+
+	result := TestCredentialsConcurrently(ctx, credentials, authFn, "mysql", testConfig)
+
+	if result.Success {
+		common.LogSuccess(i18n.Tr("mysql_credential", target, result.Username, result.Password))
+	}
+
+	return result
+}
+
+// createAuthFunc 创建MySQL认证函数
+func (p *MySQLPlugin) createAuthFunc(info *common.HostInfo, config *common.Config, state *common.State) AuthFunc {
+	return func(ctx context.Context, cred Credential) *AuthResult {
+		return p.doMySQLAuth(ctx, info, cred, config, state)
+	}
+}
+
+// doMySQLAuth 执行MySQL认证
+func (p *MySQLPlugin) doMySQLAuth(ctx context.Context, info *common.HostInfo, cred Credential, config *common.Config, state *common.State) *AuthResult {
+	connStr := fmt.Sprintf("%s:%s@tcp(%s:%d)/information_schema?charset=utf8&timeout=%ds",
+		cred.Username, cred.Password, info.Host, info.Port, int64(config.Timeout.Seconds()))
+
+	db, err := sql.Open("mysql", connStr)
+	if err != nil {
+		state.IncrementTCPFailedPacketCount()
+		return &AuthResult{
+			Success:   false,
+			ErrorType: classifyMySQLErrorType(err),
+			Error:     err,
+		}
+	}
+
+	db.SetConnMaxLifetime(config.Timeout)
+	db.SetMaxOpenConns(1)
+	db.SetMaxIdleConns(0)
+
+	err = db.PingContext(ctx)
+	if err != nil {
+		_ = db.Close()
+		state.IncrementTCPFailedPacketCount()
+		return &AuthResult{
+			Success:   false,
+			ErrorType: classifyMySQLErrorType(err),
+			Error:     err,
+		}
+	}
+
+	state.IncrementTCPSuccessPacketCount()
+
+	// MySQL 使用 sql.DB，包装为 io.Closer
+	return &AuthResult{
+		Success:   true,
+		Conn:      &sqlDBWrapper{db},
+		ErrorType: ErrorTypeUnknown,
+		Error:     nil,
+	}
+}
+
+// sqlDBWrapper 包装 sql.DB 以实现 io.Closer
+type sqlDBWrapper struct {
+	*sql.DB
+}
+
+func (w *sqlDBWrapper) Close() error {
+	return w.DB.Close()
+}
+
+// classifyMySQLErrorType MySQL错误分类
+func classifyMySQLErrorType(err error) ErrorType {
+	if err == nil {
+		return ErrorTypeUnknown
+	}
+
+	mysqlAuthErrors := []string{
+		"access denied for user",
+		"unknown database",
+		"host is not allowed",
+		"authentication failed",
+		"permission denied",
+		"user does not exist",
+	}
+
+	mysqlNetworkErrors := append(CommonNetworkErrors,
+		"too many connections",
+		"can't connect to mysql server",
+		"lost connection to mysql server",
+		"mysql server has gone away",
+	)
+
+	return ClassifyError(err, mysqlAuthErrors, mysqlNetworkErrors)
+}
+
+func (p *MySQLPlugin) identifyService(info *common.HostInfo, config *common.Config) *ScanResult {
+	target := info.Target()
+
+	conn, err := common.SafeTCPDial(target, config.Timeout)
+	if err != nil {
+		return &ScanResult{
+			Success: false,
+			Service: "mysql",
+			Error:   err,
+		}
+	}
+	defer func() { _ = conn.Close() }()
+
+	if banner := p.readMySQLBanner(conn, config); banner != "" {
+		common.LogSuccess(i18n.Tr("mysql_service", target, banner))
+		return &ScanResult{
+			Type:    plugins.ResultTypeService,
+			Success: true,
+			Service: "mysql",
+			Banner:  banner,
+		}
+	}
+
+	return &ScanResult{
+		Success: false,
+		Service: "mysql",
+		Error:   fmt.Errorf("无法识别为MySQL服务"),
+	}
+}
+
+func (p *MySQLPlugin) readMySQLBanner(conn net.Conn, config *common.Config) string {
+	_ = conn.SetReadDeadline(time.Now().Add(config.Timeout))
+
+	handshake := make([]byte, 256)
+	n, err := conn.Read(handshake)
+	if err != nil || n < 10 {
+		return ""
+	}
+
+	if handshake[4] != 10 {
+		return ""
+	}
+
+	versionStart := 5
+	versionEnd := versionStart
+	for versionEnd < n && handshake[versionEnd] != 0 {
+		versionEnd++
+	}
+
+	if versionEnd <= versionStart {
+		return ""
+	}
+
+	versionStr := string(handshake[versionStart:versionEnd])
+	return fmt.Sprintf("MySQL %s", versionStr)
+}
+
+func init() {
+	RegisterPluginWithPorts("mysql", func() Plugin {
+		return NewMySQLPlugin()
+	}, []int{3306, 3307, 33060})
+}