feat: dashboard UI with product cards + sparklines

src/components/Sparkline.tsx

@@ -0,0 +1,14 @@
+'use client'
+import { LineChart, Line, ResponsiveContainer, YAxis } from 'recharts'
+
+export function Sparkline({ data }: { data: Array<{ price: number; t: string }> }) {
+  if (data.length === 0) return <div className="h-10 text-xs text-zinc-500">keine Daten</div>
+  return (
+    <ResponsiveContainer width="100%" height={40}>
+      <LineChart data={data}>
+        <YAxis hide domain={['dataMin', 'dataMax']} />
+        <Line type="monotone" dataKey="price" stroke="#22c55e" strokeWidth={2} dot={false} isAnimationActive={false} />
+      </LineChart>
+    </ResponsiveContainer>
+  )
+}