feat(api): add timestamp field to LogRecord

- Add Timestamp field (int64, nanoseconds since Unix epoch) to LogRecord
- Import time package in api/types.go
- Set timestamp using time.Now().UnixNano() in NewLogRecord()
- Add test assertion to verify timestamp is set

The timestamp is now included in all JSON log outputs

Co-authored-by: Qwen-Coder <qwen-coder@alibabacloud.com>

api/types.go

@@ -1,5 +1,7 @@
 package api
 
+import "time"
+
 // ServiceLog represents internal service logging for diagnostics
 type ServiceLog struct {
 	Level     string            `json:"level"`
@@ -85,6 +87,9 @@ type LogRecord struct {
 	JA4Hash string `json:"ja4_hash"`
 	JA3     string `json:"ja3,omitempty"`
 	JA3Hash string `json:"ja3_hash,omitempty"`
+
+	// Timestamp in nanoseconds since Unix epoch
+	Timestamp int64 `json:"timestamp"`
 }
 
 // OutputConfig defines configuration for a single log output
@@ -212,6 +217,7 @@ func NewLogRecord(ch TLSClientHello, fp *Fingerprints) LogRecord {
 		TCPMSS:     mssPtr,
 		TCPWScale:  wScalePtr,
 		TCPOptions: opts,
+		Timestamp:  time.Now().UnixNano(),
 	}
 
 	if fp != nil {