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.

Commencez par localiser la section Settings → Storage and Data et examinez comment sont construits ses cartes arrondies et ses contrôles de type toggle existants. Mettez ensuite à jour le style des boutons “Set To Default” et “Change Directory” afin qu’il corresponde à ce langage visuel, puis vérifiez leur espacement, leur apparence et la hiérarchie des actions principales dans l’interface Settings.

Rédigé par le modèle d'indexation à partir du texte de l'issue.