Refactor impersonation mode into guard

apps/client/src/app/components/user-account-settings/user-account-settings.html

@@ -4,16 +4,29 @@
     <div class="col">
       <div class="d-flex py-1">
         <div class="w-100">
-          <div class="d-flex mb-2">
+          <div
+            class="d-flex"
+            [class.mb-2]="!hasImpersonationId"
+            [class.mb-4]="hasImpersonationId"
+          >
             <div class="align-items-center d-flex pt-1 pt-1 w-50">
               <ng-container i18n>Base Currency</ng-container>
             </div>
             <div class="pl-1 w-50" [formGroup]="baseCurrencyForm">
-              <mat-form-field appearance="outline" class="w-100 without-hint">
+              <mat-form-field
+                appearance="outline"
+                class="w-100"
+                [class.without-hint]="!hasImpersonationId"
+              >
                 <gf-currency-selector
                   formControlName="baseCurrency"
                   [currencies]="currencies"
                 />
+                @if (hasImpersonationId) {
+                  <mat-hint class="mt-1 text-muted" i18n
+                    >Derived from the portfolio you are viewing</mat-hint
+                  >
+                }
               </mat-form-field>
             </div>
           </div>