Chore: Updated mat inputs to better match the style guide. Removed placeholders in favour of labels.

overlord/src/app/client/client-list/client-list.component.html

@@ -1,7 +1,7 @@
-<mat-card appearance="outlined">
-  <mat-card-title-group>
+<mat-card>
+  <mat-card-header>
     <mat-card-title>Clients</mat-card-title>
-  </mat-card-title-group>
+  </mat-card-header>
   <mat-card-content>
     <mat-table #table [dataSource]="dataSource" matSort aria-label="Elements">
       <!-- Code Column -->