Improve UI consistency of "Set Default" and "Change Directory" buttons in Settings

## Description

In the **Settings → Storage and Data** section, the buttons **"Set To Default"** and **"Change Directory"** appear as default Flutter buttons.

They look visually inconsistent with the rest of the settings UI, which uses rounded cards and toggle-style controls.

## Current Behavior

The buttons appear large and flat, making them look different from the rest of the interface.

## Proposed Improvement

Improve the styling of these buttons so they better match the existing design language.

Possible improvements:

* Use rounded or pill-style buttons
* Improve spacing and layout
* Make "Change Directory" the primary action

## Screenshot


If this change is acceptable, I would be happy to work on implementing it.

Comienza ubicando la sección Settings → Storage and Data e inspecciona cómo están construidas sus tarjetas redondeadas y sus controles de estilo toggle existentes. Actualiza el estilo de los botones “Set To Default” y “Change Directory” para que se ajusten a ese lenguaje de diseño y, después, verifica su espaciado, apariencia y jerarquía de acción principal en la interfaz de Settings.

Escrito por el modelo de indexación a partir del texto del issue.