feat(client+home): single-instance family relations + DSC verified badge

- Family member dialog: disable Father / Mother / Spouse in the Relationship
  dropdown when one is already added to the client. Son, daughter, brother
  etc. stay unrestricted. Editing a member keeps its own current relation
  selectable. Hint added below the field.
- Home welcome banner: render a small green "DSC Verified" pill next to the
  username when GET /v1/dsc/me returns at least one ACTIVE certificate.
  Tooltip surfaces the masked serial. Silent when no DSC is mapped.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

src/app/home/home.component.html

@@ -13,6 +13,15 @@
       <div class="welcome-greeting">
         <h2>
           {{ 'labels.text.Welcome' | translate }}, <strong>{{ username }}</strong>
+          @if (dscMapped) {
+            <span class="dsc-badge" [matTooltip]="'DSC verified · serial ' + dscSerial" matTooltipPosition="right">
+              <span class="dsc-badge__shield">
+                <fa-icon icon="shield-alt"></fa-icon>
+                <span class="dsc-badge__check"><fa-icon icon="check"></fa-icon></span>
+              </span>
+              <span class="dsc-badge__label">DSC Verified</span>
+            </span>
+          }
         </h2>
         <p class="welcome-sub">{{ tenant | titlecase }} &middot; CBSNexora Core Banking Platform</p>
       </div>