chore(default-theme): styling patches

Should show correct system icon (dark):

<img width="246" height="342" alt="Image" src="https://github.com/user-attachments/assets/08b7a35d-2fd6-4bc9-aedb-61558a1d4f32" />

Left align sidebar items:

<img width="480" height="302" alt="Image" src="https://github.com/user-attachments/assets/93a7e005-f496-4d81-a54f-2ace9569ec65" />