feat: Update header logo icon for improved visual representation

Author: stephanebouget

src/app/shared/components/header/header.component.html

@@ -1,6 +1,6 @@
 <div class="header">
-  <div class="header-left" (click)="showAlerts()" style="cursor: pointer;">
-    <i class="ti ti-lock logo"></i>
+  <div class="header-left" (click)="showAlerts()" style="cursor: pointer">
+    <i class="ti ti-shield-half-filled logo"></i>
     <span class="title">GitHub Alerts</span>
   </div>
   <div class="header-right" *ngIf="authenticated">