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/Card.astro

@@ -2,18 +2,18 @@
 // Composable card container (.card). For the fixed demo-showcase card see ../cards/Card.astro.
 
 interface Props {
-	/** element to render instead of div (e.g. form, a) */
-	as?: string;
-	/** card-{size} body padding: sm | md | lg */
-	size?: string;
-	class?: string;
-	/** remaining attributes (id, action, data-*, …) are forwarded to the element */
-	[key: string]: unknown;
+  /** element to render instead of div (e.g. form, a) */
+  as?: string
+  /** card-{size} body padding: sm | md | lg */
+  size?: string
+  class?: string
+  /** remaining attributes (id, action, data-*, …) are forwarded to the element */
+  [key: string]: unknown
 }
 
-const { as: Element = 'div', size, class: className, ...rest } = Astro.props;
+const { as: Element = 'div', size, class: className, ...rest } = Astro.props
 ---
 
 <Element class:list={['card', size && `card-${size}`, className]} {...rest}>
-	<slot />
+  <slot />
 </Element>