refactor: address loading review findings (#18)

frontend/src/app/components/lease-form/lease-form.css

@@ -28,17 +28,6 @@
   border-radius: 22px;
   background: var(--surface);
 }
-fieldset {
-  min-width: 0;
-  margin: 0;
-  padding: 0;
-  border: 0;
-}
-.primary-action mat-spinner {
-  display: inline-block;
-  margin-right: 8px;
-  vertical-align: middle;
-}
 .guarantor-section {
   margin-top: 18px;
 }

frontend/src/app/components/lease-form/lease-form.html

@@ -29,7 +29,10 @@
     @if (error()) {
       <div class="alert-error" role="alert">{{ error() }}</div>
     }
-    <fieldset [disabled]="saving()" [attr.inert]="saving() ? '' : null">
+    <p class="visually-hidden" role="status" aria-live="polite">
+      {{ saving() ? 'Enregistrement en cours.' : '' }}
+    </p>
+    <fieldset class="busy-fieldset" [disabled]="saving()" [attr.inert]="saving() ? '' : null">
       <section class="form-section">
         <div class="section-heading">
           <span>01</span>
@@ -143,7 +146,7 @@
       </section>
     </fieldset>
   </form>
-  <fieldset [disabled]="saving()" [attr.inert]="saving() ? '' : null">
+  <fieldset class="busy-fieldset" [disabled]="saving()" [attr.inert]="saving() ? '' : null">
     <section class="guarantor-section">
       <div class="section-heading">
         <span>03</span>
@@ -171,7 +174,7 @@
       class="primary-action"
       [disabled]="saving()"
     >
-      <span aria-live="polite">
+      <span>
         @if (saving()) {
           <mat-spinner diameter="18" aria-hidden="true" /> Enregistrement…
         } @else {