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/cassandra.go

@@ -0,0 +1,217 @@
+//go:build plugin_cassandra || !plugin_selective
+
+package services
+
+import (
+	"context"
+	"fmt"
+	"strings"
+
+	"github.com/gocql/gocql"
+	"github.com/shadow1ng/fscan/common"
+	"github.com/shadow1ng/fscan/common/i18n"
+	"github.com/shadow1ng/fscan/plugins"
+)
+
+// CassandraPlugin Cassandra扫描插件
+type CassandraPlugin struct {
+	plugins.BasePlugin
+}
+
+func NewCassandraPlugin() *CassandraPlugin {
+	return &CassandraPlugin{
+		BasePlugin: plugins.NewBasePlugin("cassandra"),
+	}
+}
+
+func (p *CassandraPlugin) Scan(ctx context.Context, info *common.HostInfo, config *common.Config, state *common.State) *ScanResult {
+	target := info.Target()
+
+	if config.DisableBrute {
+		return p.identifyService(ctx, info, config, state)
+	}
+
+	// 先尝试无认证连接
+	if result := p.tryNoAuthConnection(ctx, info, config, state); result != nil && result.Success {
+		return result
+	}
+
+	credentials := GenerateCredentials("cassandra", config)
+	if len(credentials) == 0 {
+		return &ScanResult{
+			Success: false,
+			Service: "cassandra",
+			Error:   fmt.Errorf("没有可用的测试凭据"),
+		}
+	}
+
+	// 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, "cassandra", testConfig)
+
+	if result.Success {
+		common.LogSuccess(i18n.Tr("cassandra_credential", target, result.Username, result.Password))
+	}
+
+	return result
+}
+
+// createAuthFunc 创建Cassandra认证函数
+func (p *CassandraPlugin) createAuthFunc(info *common.HostInfo, config *common.Config, state *common.State) AuthFunc {
+	return func(ctx context.Context, cred Credential) *AuthResult {
+		return p.doCassandraAuth(ctx, info, cred, config, state)
+	}
+}
+
+// doCassandraAuth 执行Cassandra认证
+func (p *CassandraPlugin) doCassandraAuth(ctx context.Context, info *common.HostInfo, cred Credential, config *common.Config, state *common.State) *AuthResult {
+	cluster := gocql.NewCluster(info.Host)
+	cluster.Port = info.Port
+	cluster.Timeout = config.Timeout
+	cluster.ConnectTimeout = config.Timeout
+
+	if cred.Username != "" || cred.Password != "" {
+		cluster.Authenticator = gocql.PasswordAuthenticator{
+			Username: cred.Username,
+			Password: cred.Password,
+		}
+	}
+
+	session, err := cluster.CreateSession()
+	if err != nil {
+		state.IncrementTCPFailedPacketCount()
+		return &AuthResult{
+			Success:   false,
+			ErrorType: classifyCassandraErrorType(err),
+			Error:     err,
+		}
+	}
+	state.IncrementTCPSuccessPacketCount()
+
+	var dummy string
+	err = session.Query("SELECT cluster_name FROM system.local").WithContext(ctx).Scan(&dummy)
+	if err != nil {
+		session.Close()
+		return &AuthResult{
+			Success:   false,
+			ErrorType: classifyCassandraErrorType(err),
+			Error:     err,
+		}
+	}
+
+	return &AuthResult{
+		Success:   true,
+		Conn:      &cassandraSessionWrapper{session},
+		ErrorType: ErrorTypeUnknown,
+		Error:     nil,
+	}
+}
+
+// cassandraSessionWrapper 包装 gocql.Session 以实现 io.Closer
+type cassandraSessionWrapper struct {
+	*gocql.Session
+}
+
+func (w *cassandraSessionWrapper) Close() error {
+	w.Session.Close()
+	return nil
+}
+
+// classifyCassandraErrorType Cassandra错误分类
+func classifyCassandraErrorType(err error) ErrorType {
+	if err == nil {
+		return ErrorTypeUnknown
+	}
+
+	cassandraAuthErrors := []string{
+		"authentication failed",
+		"bad credentials",
+		"invalid credentials",
+		"username and/or password are incorrect",
+		"unauthorized",
+		"access denied",
+	}
+
+	return ClassifyError(err, cassandraAuthErrors, CommonNetworkErrors)
+}
+
+// tryNoAuthConnection 尝试无认证连接
+func (p *CassandraPlugin) tryNoAuthConnection(ctx context.Context, info *common.HostInfo, config *common.Config, state *common.State) *ScanResult {
+	target := info.Target()
+
+	cluster := gocql.NewCluster(info.Host)
+	cluster.Port = info.Port
+	cluster.Timeout = config.Timeout
+	cluster.ConnectTimeout = config.Timeout
+
+	session, err := cluster.CreateSession()
+	if err != nil {
+		state.IncrementTCPFailedPacketCount()
+		return nil
+	}
+	state.IncrementTCPSuccessPacketCount()
+
+	var dummy string
+	err = session.Query("SELECT cluster_name FROM system.local").WithContext(ctx).Scan(&dummy)
+	if err != nil {
+		session.Close()
+		return nil
+	}
+
+	session.Close()
+	common.LogSuccess(i18n.Tr("cassandra_unauth", target))
+	return &ScanResult{
+		Type:    plugins.ResultTypeService,
+		Success: true,
+		Service: "cassandra",
+		Banner:  fmt.Sprintf("Cassandra (无认证, 集群: %s)", dummy),
+	}
+}
+
+func (p *CassandraPlugin) identifyService(ctx context.Context, info *common.HostInfo, config *common.Config, state *common.State) *ScanResult {
+	target := info.Target()
+
+	cluster := gocql.NewCluster(info.Host)
+	cluster.Port = info.Port
+	cluster.Timeout = config.Timeout
+	cluster.ConnectTimeout = config.Timeout
+
+	session, err := cluster.CreateSession()
+	if err != nil {
+		state.IncrementTCPFailedPacketCount()
+		if strings.Contains(strings.ToLower(err.Error()), "authentication") {
+			banner := "Cassandra (需要认证)"
+			common.LogSuccess(i18n.Tr("cassandra_service", target, banner))
+			return &ScanResult{
+				Type:    plugins.ResultTypeService,
+				Success: true,
+				Service: "cassandra",
+				Banner:  banner,
+			}
+		}
+		return &ScanResult{
+			Success: false,
+			Service: "cassandra",
+			Error:   err,
+		}
+	}
+	state.IncrementTCPSuccessPacketCount()
+	session.Close()
+
+	banner := "Cassandra"
+	common.LogSuccess(i18n.Tr("cassandra_service", target, banner))
+	return &ScanResult{
+		Type:    plugins.ResultTypeService,
+		Success: true,
+		Service: "cassandra",
+		Banner:  banner,
+	}
+}
+
+func init() {
+	RegisterPluginWithPorts("cassandra", func() Plugin {
+		return NewCassandraPlugin()
+	}, []int{9042, 9160, 7000, 7001})
+}