feat: update cirBTC logo for ARC

[maxime-oe]

Using square SVG with the perspective that it will be rounded same way as USDC and EURC

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Note

Low Risk
Single static SVG asset swap with no application or contract logic changes.

Overview
Replaces the cirBTC token icon at icons/eip155:5042/erc20:0x171A4217b86A807A64eB94757Db6849fb4bDbAA0.svg with a new 120×120 square SVG meant to match how USDC and EURC are cropped/rounded in the UI.

The old asset was a 640×640 export with a flat #0B53BF fill and heavy Lottie-style path markup. The new one uses a purple→blue linear gradient background and simplified white mark paths (ARC/cirBTC branding).

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