refactor(auth): extract timestamp validation to separate function

Move timestamp validation logic from handlers to ValidateTimeStamp function in auth.go to avoid code duplication and improve maintainability

handlers.go

@@ -54,9 +54,8 @@ func RegisterHandler(w http.ResponseWriter, r *http.Request) {
 		return
 	}
 
-	currentTime := time.Now().UnixMilli()
-	if !globalConfig.Debug && (currentTime-req.TimeStamp > 3000 || req.TimeStamp-currentTime > 3000) {
-		SendErrorResponse(w, http.StatusBadRequest, "timestamp out of valid range")
+	if err := ValidateTimeStamp(req.TimeStamp); err != nil {
+		SendErrorResponse(w, http.StatusBadRequest, err.Error())
 		return
 	}
 
@@ -128,9 +127,8 @@ func LoginHandler(w http.ResponseWriter, r *http.Request) {
 		return
 	}
 
-	currentTime := time.Now().UnixMilli()
-	if !globalConfig.Debug && (currentTime-req.TimeStamp > 3000 || req.TimeStamp-currentTime > 3000) {
-		SendErrorResponse(w, http.StatusBadRequest, "timestamp out of valid range")
+	if err := ValidateTimeStamp(req.TimeStamp); err != nil {
+		SendErrorResponse(w, http.StatusBadRequest, err.Error())
 		return
 	}
 
@@ -227,9 +225,8 @@ func ValidateRequestWithBody(w http.ResponseWriter, r *http.Request, body []byte
 		return 0, "", errors.New("timeStamp is required")
 	}
 
-	currentTime := time.Now().UnixMilli()
-	if !globalConfig.Debug && (currentTime-int64(timeStamp) > 3000 || int64(timeStamp)-currentTime > 3000) {
-		return 0, "", errors.New("timestamp out of valid range")
+	if err := ValidateTimeStamp(int64(timeStamp)); err != nil {
+		return 0, "", err
 	}
 
 	userID, err := extractUserIDFromToken(token)