chore: add vitest/globals types, remove redundant vitest imports, fix pre-existing lint issues

src/widgets/Navigation/ui/SidebarNav.tsx

@@ -1,6 +1,6 @@
 'use client';
 
-import { useState, useEffect } from 'react';
+import { useEffect, useState } from 'react';
 import { cn } from '$shared/lib';
 import type { NavItem } from '../model/types';
 
@@ -31,7 +31,9 @@ export function SidebarNav({ items }: Props) {
 
     items.forEach((item) => {
       const el = document.getElementById(item.id);
-      if (el) observer.observe(el);
+      if (el) {
+        observer.observe(el);
+      }
     });
 
     return () => observer.disconnect();
@@ -62,6 +64,7 @@ export function SidebarNav({ items }: Props) {
           const isActive = activeSection === item.id;
           return (
             <button
+              type="button"
               key={item.id}
               onClick={() => scrollToSection(item.id)}
               className={cn(