Align POS header with other apps: AI assistant, register button, sidebar

- Add the Afia AI assistant to the header (topbar AI button + slide-over),
  matching every other Ladill app. Ports config/afia.php, AfiaService, a POS
  AiController (pos.ai.chat) scoped to register/sales/products, and includes
  the slide-over in the app layout. The afia() Alpine component already existed.
- Hide the header "Open register" button while on the register page.
- Move Settings to a pinned bottom section of the sidebar, like other apps.
- Commit the updated POS logo + launcher icon assets.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

resources/views/components/app-layout.blade.php

@@ -27,5 +27,6 @@
             </main>
         </div>
     </div>
+    @include('partials.afia')
 </body>
 </html>