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）

tools/perftest/results/param_tests/mt_results.csv

@@ -0,0 +1,6 @@
+"module_threads","duration_ms","packets_per_sec","tcp_success","tcp_failed","success_rate"
+"5","15211","83.49","759","511","59.76"
+"10","15253","83.26","759","511","59.76"
+"20","15221","83.44","759","511","59.76"
+"50","15254","83.26","759","511","59.76"
+"100","15217","83.46","759","511","59.76"

tools/perftest/results/param_tests/time_results.csv

@@ -0,0 +1,5 @@
+"time_seconds","duration_ms","packets_per_sec","tcp_success","tcp_failed","success_rate"
+"1","13110","96.87","759","511","59.76"
+"2","13295","95.52","759","511","59.76"
+"3","15231","83.38","759","511","59.76"
+"5","16451","77.20","759","511","59.76"