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。

common/output/stdout_writer_test.go

@@ -0,0 +1,35 @@
+package output
+
+import "testing"
+
+func TestSplitHostPort(t *testing.T) {
+	tests := []struct {
+		name     string
+		target   string
+		wantHost string
+		wantPort int
+		wantOK   bool
+	}{
+		{name: "ipv4", target: "192.168.1.1:80", wantHost: "192.168.1.1", wantPort: 80, wantOK: true},
+		{name: "hostname", target: "example.com:443", wantHost: "example.com", wantPort: 443, wantOK: true},
+		{name: "bracketed ipv6", target: "[2001:db8::1]:8443", wantHost: "2001:db8::1", wantPort: 8443, wantOK: true},
+		{name: "bare ipv6 without port", target: "2001:db8::1", wantOK: false},
+		{name: "invalid port", target: "example.com:abc", wantOK: false},
+		{name: "port out of range", target: "example.com:65536", wantOK: false},
+	}
+
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			host, port, ok := splitHostPort(tt.target)
+			if ok != tt.wantOK {
+				t.Fatalf("splitHostPort(%q) ok = %v, want %v", tt.target, ok, tt.wantOK)
+			}
+			if !ok {
+				return
+			}
+			if host != tt.wantHost || port != tt.wantPort {
+				t.Fatalf("splitHostPort(%q) = (%q, %d), want (%q, %d)", tt.target, host, port, tt.wantHost, tt.wantPort)
+			}
+		})
+	}
+}