feat(handlers): add duplicate login check and improve request handling

refactor: move postLog package to root directory and enhance logging
fix(frpc): improve request parsing and type handling for instance creation
chore: update config paths and enable debug mode

handlers.go

@@ -7,7 +7,7 @@ import (
 	"io"
 	"net/http"
 	"strconv"
-	"super-frpc/modules"
+	"super-frpc/postLog"
 	"time"
 )
 
@@ -150,6 +150,12 @@ func LoginHandler(w http.ResponseWriter, r *http.Request) {
 		return
 	}
 
+	existingTokenInfo, err := GetTokenInfo(user.UserID)
+	if err == nil && existingTokenInfo != nil {
+		SendErrorResponse(w, http.StatusConflict, "user is already logged in")
+		return
+	}
+
 	token, err := GenerateToken(user.UserID)
 	if err != nil {
 		SendErrorResponse(w, http.StatusInternalServerError, "failed to generate token")