Update DOT logo

**old**
<img width="496" height="64" alt="Image" src="https://github.com/user-attachments/assets/4422387b-ba98-47c9-8785-9c36e4781484" />

**new**
<img width="348" height="120" alt="Image" src="https://github.com/user-attachments/assets/bedcc726-1088-4619-85af-0806f1720bcd" />


[Branding ressources](https://github.com/Tomen/polkadot-second-age-brand-kit/tree/main/icon/svg)