feat: 统一服务缓存 + 指纹驱动插件匹配

将 webServiceCache 扩展为通用 serviceCache，所有指纹识别结果
统一缓存，插件匹配时端口不命中则回退到服务名称匹配。

删除多余的 service_cache.go，复用已有的 ServiceInfo 体系。
补充 nil 防御、Explicit 标记、大量单元/集成/回归测试。

web/api/result.go

@@ -7,9 +7,11 @@ import (
 	"encoding/csv"
 	"encoding/json"
 	"fmt"
+	"net"
 	"net/http"
 	"os"
 	"path/filepath"
+	"strconv"
 	"strings"
 	"sync"
 	"time"
@@ -393,18 +395,39 @@ func (h *ResultHandler) Export(w http.ResponseWriter, r *http.Request) {
 
 // extractPort 从 "ip:port" 中提取端口
 func extractPort(target string) string {
-	if idx := strings.LastIndex(target, ":"); idx != -1 {
-		return target[idx+1:]
+	_, port, ok := splitTargetHostPort(target)
+	if !ok {
+		return ""
 	}
-	return ""
+	return port
 }
 
 // extractHost 从 "ip:port" 中提取主机
 func extractHost(target string) string {
-	if idx := strings.LastIndex(target, ":"); idx != -1 {
-		return target[:idx]
+	host, _, ok := splitTargetHostPort(target)
+	if !ok {
+		return target
 	}
-	return target
+	return host
+}
+
+func splitTargetHostPort(target string) (string, string, bool) {
+	host, port, err := net.SplitHostPort(target)
+	if err != nil {
+		if strings.Count(target, ":") != 1 {
+			return "", "", false
+		}
+		parts := strings.SplitN(target, ":", 2)
+		host, port = parts[0], parts[1]
+	}
+	if host == "" || port == "" {
+		return "", "", false
+	}
+	portNum, err := strconv.Atoi(port)
+	if err != nil || portNum < 1 || portNum > 65535 {
+		return "", "", false
+	}
+	return host, port, true
 }
 
 // extractServiceInfo 从 details 中提取服务信息

web/api/result_test.go

@@ -0,0 +1,31 @@
+//go:build web
+
+package api
+
+import "testing"
+
+func TestExtractHostPortIPv6(t *testing.T) {
+	tests := []struct {
+		name     string
+		target   string
+		wantHost string
+		wantPort string
+	}{
+		{name: "ipv4", target: "192.168.1.1:80", wantHost: "192.168.1.1", wantPort: "80"},
+		{name: "hostname", target: "example.com:443", wantHost: "example.com", wantPort: "443"},
+		{name: "bracketed ipv6", target: "[2001:db8::1]:8443", wantHost: "2001:db8::1", wantPort: "8443"},
+		{name: "bare ipv6 without port", target: "2001:db8::1", wantHost: "2001:db8::1", wantPort: ""},
+		{name: "invalid port", target: "example.com:abc", wantHost: "example.com:abc", wantPort: ""},
+	}
+
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			if got := extractHost(tt.target); got != tt.wantHost {
+				t.Fatalf("extractHost(%q) = %q, want %q", tt.target, got, tt.wantHost)
+			}
+			if got := extractPort(tt.target); got != tt.wantPort {
+				t.Fatalf("extractPort(%q) = %q, want %q", tt.target, got, tt.wantPort)
+			}
+		})
+	}
+}