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/benchmarks/benchmark_results.txt

@@ -0,0 +1,22 @@
+BenchmarkCheckSum-24                      	659448997	         1.821 ns/op	       0 B/op	       0 allocs/op
+BenchmarkArrayCountValueTop-24            	    4047	    257006 ns/op	  329822 B/op	    5040 allocs/op
+BenchmarkTCPDial-24                       	    4596	    473517 ns/op	    2424 B/op	      27 allocs/op
+BenchmarkResultCollectorAdd-24            	31689693	        42.06 ns/op	      99 B/op	       0 allocs/op
+BenchmarkResultCollectorAddParallel-24    	16319025	        73.03 ns/op	      99 B/op	       0 allocs/op
+BenchmarkResultCollectorGetAll-24         	  501963	      2320 ns/op	   16384 B/op	       1 allocs/op
+BenchmarkFailedPortCollectorAdd-24        	18020209	        72.26 ns/op	     218 B/op	       0 allocs/op
+BenchmarkEstimateScanTime-24              	1000000000	         0.1474 ns/op	       0 B/op	       0 allocs/op
+BenchmarkCalculateTotalTasks-24           	  345832	      3346 ns/op	       0 B/op	       0 allocs/op
+BenchmarkBuildExcludeMap-24               	 8549785	       143.4 ns/op	     328 B/op	       3 allocs/op
+ok  	github.com/shadow1ng/fscan/core	14.384s
+BenchmarkDecodePattern-24            	23028650	        44.72 ns/op	      56 B/op	       3 allocs/op
+BenchmarkDecodePattern_Complex-24    	 8355910	       144.3 ns/op	      40 B/op	      13 allocs/op
+ok  	github.com/shadow1ng/fscan/core/portfinger	3.008s
+BenchmarkParseIPCIDR24-24      	   40768	     29300 ns/op	   57881 B/op	     294 allocs/op
+BenchmarkParseIPCIDR16-24      	     829	   1394559 ns/op	 2692984 B/op	   10122 allocs/op
+BenchmarkParseIPRange-24       	   42494	     28765 ns/op	   57816 B/op	     289 allocs/op
+BenchmarkParseIPSingle-24      	15086103	        76.51 ns/op	      64 B/op	       4 allocs/op
+BenchmarkParsePortRange-24     	     303	   4050534 ns/op	10277983 B/op	     585 allocs/op
+BenchmarkParsePortList-24      	 1667944	       700.6 ns/op	     968 B/op	      14 allocs/op
+BenchmarkParsePortCommon-24    	 1007536	      1237 ns/op	    1672 B/op	      16 allocs/op
+ok  	github.com/shadow1ng/fscan/common/parsers	11.298s

tools/perftest/results/cloudflare_anycast/perf_results.csv

@@ -0,0 +1,11 @@
+"threads","duration_sec","ports_per_sec","total_ports"
+"200","30.221","42","1270"
+"400","19.124","66.4","1270"
+"600","16.162","78.6","1270"
+"800","14.099","90.1","1270"
+"1000","12.127","104.7","1270"
+"1500","12.102","104.9","1270"
+"2000","12.114","104.8","1270"
+"3000","12.122","104.8","1270"
+"4000","12.074","105.2","1270"
+"5000","12.116","104.8","1270"

tools/perftest/results/internal_metrics/precise_results.csv

@@ -0,0 +1,8 @@
+"threads","duration_ms","packets_per_sec","total_packets","tcp_success","tcp_failed","success_rate"
+200,29330,43.3,1270,759,511,59.8
+400,18730,67.8,1270,759,511,59.8
+600,15270,83.2,1270,759,511,59.8
+800,13090,97.2,1270,759,511,59.8
+1000,11660,109.0,1270,759,511,59.8
+1500,11500,110.9,1270,759,511,59.8
+2000,11900,106.8,1270,759,511,59.8

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"