Add concept of platforms

apps/client/src/app/pages/faq/self-hosting/self-hosting-page.html

@@ -86,6 +86,17 @@
           </ol>
         </mat-card-content>
       </mat-card>
+      <mat-card appearance="outlined" class="mb-3">
+        <mat-card-header>
+          <mat-card-title>What is the concept of platforms?</mat-card-title>
+        </mat-card-header>
+        <mat-card-content>
+          Platforms are used to group multiple accounts, such as a savings
+          account and a trading account at the same bank. By assigning accounts
+          to the same platform, they are displayed with a unified icon and you
+          gain insights into platform-specific risks.
+        </mat-card-content>
+      </mat-card>
       <mat-card appearance="outlined" class="mb-3">
         <mat-card-header>
           <mat-card-title>How do I add a new platform?</mat-card-title>