🚚 reconstructing and fixing file structures

The reconstruction includes moving the Navbar component from shared to widget because Navbar is a group of elements, and
removing the login-signup form due to changes in logic that will use a popup flow to improve the user experience without
navigating to another page for authentication.

app/(main)/layout.tsx

@@ -1,4 +1,4 @@
-import NavbarUI from "@/shared/ui/navbar";
+import NavbarUI from "@/widgets/navbar/ui/Navbar";
 import React from "react";
 
 const mainLayout = ({ children }: Readonly<{ children: React.ReactNode }>) => {