style(frontend): fix wallet connect qr btn style (#3138)

# Motivation

The text color of the wallet connect modal button is not readable. For
now, in coordination with the design team we display a primary button.

# Changes

Use btn component for Wallet connect modal QR code

# Tests

Text marked so we see that it is there:
<img width="549" alt="image"
src="https://github.com/user-attachments/assets/a2052373-5e5b-4d74-b668-416387207b2f">
No text showing:
<img width="591" alt="image"
src="https://github.com/user-attachments/assets/3f5d0409-f338-4f32-9721-cdf4edeb5215">


<img width="542" alt="image"
src="https://github.com/user-attachments/assets/9a815d71-b8e7-4e6a-9bc6-d594469a6ee5">

src/frontend/src/eth/components/wallet-connect/WalletConnectForm.svelte

@@ -73,11 +73,12 @@
 		{/if}
 
 		{#if !renderQRCodeReader}
-			<button
+			<Button
 				type="button"
-				class="wallet-connect inset-center text-center font-bold text-white"
-				style="padding: var(--padding) var(--padding-3x)"
-				on:click={() => (renderQRCodeReader = true)}>{$i18n.wallet_connect.text.scan_qr}</button
+				styleClass="inset-center"
+				colorStyle="primary"
+				paddingSmall
+				on:click={() => (renderQRCodeReader = true)}>{$i18n.wallet_connect.text.scan_qr}</Button
 			>
 		{/if}
 	</div>