feat: TUI visual improvements (nav bar, flow details) and timestamp support

internal/sip/parser.go

@@ -3,6 +3,7 @@ package sip
 import (
 	"regexp"
 	"strings"
+	"time"
 )
 
 // Method represents a SIP method
@@ -27,6 +28,7 @@ const (
 
 // Packet represents a parsed SIP packet
 type Packet struct {
+	Timestamp  time.Time
 	Raw        string
 	IsRequest  bool
 	Method     Method