[ui] redesign UX for navbar

frontend/src/app/components/master-page/master-page.component.html

@@ -1,7 +1,8 @@
 <app-menu *ngIf="servicesEnabled" (loggedOut)="onLoggedOut()"></app-menu>
 
 <ng-container *ngIf="{ val: network$ | async } as network">
-<header *ngIf="headerVisible" style="position: fixed; width: 100%; z-index: 100;">
+<header *ngIf="headerVisible" class="sticky-header">
+
   <nav class="navbar navbar-expand-md navbar-dark bg-dark">
   <!-- Hamburger -->
   <ng-container *ngIf="servicesEnabled">
@@ -77,8 +78,6 @@
 </nav>
 </header>
 
-<div class="content-padding"></div>
-
 <app-testnet-alert *ngIf="network.val === 'testnet' || network.val === 'signet'"></app-testnet-alert>
 
 <main>