feat(frontend): make markers list vertical in stream page (#46)

Resolves #38

Reviewed-on: #46

frontend/src/components/CardHeader.tsx

@@ -0,0 +1,18 @@
+import type { ElementType } from "react";
+
+type Props = {
+    icon: ElementType;
+    title: string;
+    accent?: "primary" | "accent";
+};
+
+const CardHeader = ({ icon: Icon, title, accent = "primary" }: Props) => (
+    <div className="flex items-center gap-2.5">
+        <div className={`w-8 h-8 rounded-lg flex items-center justify-center flex-shrink-0 ${accent === "primary" ? "bg-terracotta/10" : "bg-olive/10"}`}>
+            <Icon size={16} className={accent === "primary" ? "text-terracotta" : "text-olive"} />
+        </div>
+        <h2 className="text-xl font-heading text-text-primary">{title}</h2>
+    </div>
+);
+
+export default CardHeader;