Add quality gates: Prettier for Astro, astro check for shared, unused SCSS variable lint (#2749)

Co-authored-by: copilot-swe-agent[bot] <198982749+Copilot@users.noreply.github.com>

shared/ui/Payment.astro

@@ -1,23 +1,18 @@
 ---
 // Equivalent of ui/payment.html
 interface Props {
-	payment?: string;
-	dark?: boolean;
-	size?: string;
-	class?: string;
+  payment?: string
+  dark?: boolean
+  size?: string
+  class?: string
 }
 
-const { payment = 'visa', dark, size, class: className } = Astro.props;
+const { payment = 'visa', dark, size, class: className } = Astro.props
 
 // Class token order exactly as in ui/payment.html. The include['size'] bug
 // (junk `payment-N`) is NOT reproduced — only an explicit `size` becomes
 // `payment-{size}`.
-const classes = [
-	'payment',
-	size && `payment-${size}`,
-	`payment-provider-${payment}${dark ? '-dark' : ''}`,
-	className,
-]
+const classes = ['payment', size && `payment-${size}`, `payment-provider-${payment}${dark ? '-dark' : ''}`, className]
 ---
 
 <span class:list={classes}></span>