perf: 六项性能优化

- DNS 解析缓存：sync.Map 缓存避免重复系统调用
- 凭据测试 TCP 预检：不可达目标直接跳过全部凭据
- Web 探测 HTTP Client 复用：全局共享连接池
- 端口扫描 Bloom Filter 去重：替代 map 降低内存
- 进度条 atomic 累加 + 50ms 节流渲染：消除锁竞争
- 服务探针预解码：Init 时预编译，运行时零解码开销

core/icmp.go

@@ -391,7 +391,7 @@ func RunIcmp1(hostslist []string, conn *icmp.PacketConn, chanHosts chan string,
 	}
 	packets := make([]icmpPacket, 0, len(hostslist))
 	for _, host := range hostslist {
-		dst, _ := net.ResolveIPAddr("ip", host)
+		dst, _ := common.DNSCache.ResolveIP(host)
 		packets = append(packets, icmpPacket{data: makemsg(host), dst: dst})
 	}