feat: add toolbar position setting and update email viewer layout

- Introduced a new setting for toolbar position in appearance settings, allowing users to choose between 'top' and 'below-subject'.
- Updated the EmailViewer component to conditionally render the toolbar based on the selected position.
- Enhanced the UI for the toolbar with action buttons for replying, archiving, and deleting emails.
- Added translations for the new toolbar position setting in multiple languages.

locales/es/common.json

@@ -487,6 +487,12 @@
       "animations": {
         "label": "Habilitar Animaciones",
         "description": "Mostrar transiciones y efectos suaves"
+      },
+      "toolbar_position": {
+        "label": "Posición de la barra de herramientas",
+        "description": "Dónde mostrar los botones de acción del correo (Responder, Archivar, Eliminar, etc.)",
+        "top": "Arriba",
+        "below_subject": "Debajo del asunto"
       }
     },
     "keywords": {