feat(lotto): 구매탭 4주 추세 차트(너 vs 큐레이터 평균 일치)

src/pages/lotto/components/PurchaseTrendChart.jsx

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+import { useEffect, useState } from 'react';
+import { getReviewHistory } from '../../../api';
+
+export default function PurchaseTrendChart() {
+    const [reviews, setReviews] = useState([]);
+    useEffect(() => {
+        getReviewHistory(4).then(rs => setReviews(rs.reverse())); // asc
+    }, []);
+
+    if (reviews.length === 0) return null;
+
+    const maxAvg = Math.max(
+        ...reviews.flatMap(r => [r.curator_avg_match || 0, r.user_avg_match || 0]),
+        2.5
+    );
+    const w = 320, h = 80, pad = 16;
+    const xs = (i) => pad + (i / Math.max(reviews.length - 1, 1)) * (w - 2 * pad);
+    const ys = (v) => v == null ? null : h - pad - (v / maxAvg) * (h - 2 * pad);
+
+    const line = (key) => reviews
+        .map((r, i) => ({ x: xs(i), y: ys(r[key]) }))
+        .filter(p => p.y != null)
+        .map((p, i) => `${i === 0 ? 'M' : 'L'}${p.x},${p.y}`)
+        .join(' ');
+
+    return (
+        <section className="lotto-panel">
+            <div className="lotto-panel__head">
+                <div>
+                    <p className="lotto-panel__eyebrow">Trend (last 4 weeks)</p>
+                    <h3>너 vs 큐레이터 평균 일치 수</h3>
+                </div>
+            </div>
+            <svg width={w} height={h} className="trend-chart">
+                <path d={line('curator_avg_match')} stroke="#b8a8ff" strokeWidth="2" fill="none" />
+                <path d={line('user_avg_match')}    stroke="#76e09a" strokeWidth="2" fill="none" />
+            </svg>
+            <div className="trend-legend">
+                <span><span className="dot dot--curator" /> 큐레이터</span>
+                <span><span className="dot dot--user" /> 너</span>
+            </div>
+        </section>
+    );
+}