ui: update header/nav style to match layout

src/components/Sidebar/styles.tsx

@@ -1,55 +0,0 @@
-import { Link } from "gatsby"
-import styled from "styled-components"
-
-export const SidebarWrapper = styled.aside`
-  width: 200px;
-`
-
-export const Logo = styled.img`
-  width: 122px;
-`
-
-export const Menu = styled.nav`
-  margin-top: 16px;
-  display: flex;
-  flex-direction: column;
-  align-items: flex-start;
-`
-
-export const MenuItem = styled(Link)`
-  display: flex;
-  align-items: center;
-  font-size: 22px;
-  text-decoration: none;
-  color: #555;
-  position: relative;
-  transition: color 0.3s;
-
-  &::after {
-    position: absolute;
-    content: "";
-    height: 2px;
-    transition: width 0.3s;
-    width: 0;
-    bottom: -3px;
-    background: #bf1e2e;
-  }
-
-  &:hover {
-    color: #bf1e2e;
-  }
-
-  &:hover::after {
-    width: calc(100% - 8px - 6px);
-  }
-
-  & + & {
-    margin-top: 8px;
-  }
-
-  svg {
-    margin-left: 6px;
-    width: 8px;
-    height: 15px;
-  }
-`