Port modular features into boursecu and fix desktop login UX.

Add support chat, piggy funds, PWA banner, notification/SSE sync, and messenger legacy guards while keeping boursecu theme; also balance login panels and unblock login navigation.

Co-authored-by: Cursor <cursoragent@cursor.com>

src/views/login/desktop/components/DesktopAuthShell.vue

@@ -1,6 +1,10 @@
 <template>
   <div class="dauth dauth--boursecu">
     <div class="dauth__layout">
+      <main class="dauth-form-panel">
+        <slot />
+      </main>
+
       <aside class="dauth-brand dauth-brand--boursecu">
         <div class="dauth-brand__pattern" />
         <div class="dauth-brand__content">
@@ -22,10 +26,6 @@
         </div>
         <div class="dauth-brand__footer">نسخه {{ version }}</div>
       </aside>
-
-      <main class="dauth-form-panel">
-        <slot />
-      </main>
     </div>
   </div>
 </template>