feat(register): integrate modal and toast services for success and error handling

src/app/shared/components/modal-shell/modal-shell.component.scss

@@ -37,6 +37,7 @@
 }
 
 .modal-shell__content {
+  min-height: 180px;
   max-height: calc(100dvh - 2rem);
   border-radius: 1.25rem;
   background:
@@ -72,6 +73,10 @@
 }
 
 .modal-shell__body {
+  flex: 1;
+  display: flex;
+  flex-direction: column;
+  justify-content: center;
   padding: 0 1.25rem 1.25rem;
   color: #303030;
 }