feat(lotto): DecisionCard + BulkPurchaseButton, BriefingTab 단일 화면 재구성

src/pages/lotto/components/decision/BulkPurchaseButton.jsx

@@ -0,0 +1,33 @@
+import { useState } from 'react';
+import { bulkPurchase } from '../../../../api';
+import { MODES } from './TierModeToggle';
+
+export default function BulkPurchaseButton({ drawNo, tierMode, onSuccess }) {
+    const [busy, setBusy] = useState(false);
+    const mode = MODES.find(m => m.key === tierMode) || MODES[0];
+
+    const onClick = async () => {
+        if (busy) return;
+        setBusy(true);
+        try {
+            await bulkPurchase({
+                draw_no: drawNo,
+                tier_mode: tierMode,
+                sets: mode.sets,
+                amount: mode.amount,
+            });
+            onSuccess?.();
+            alert(`${mode.sets}세트 구매 기록 완료!`);
+        } catch (e) {
+            alert(`구매 기록 실패: ${e?.message || e}`);
+        } finally {
+            setBusy(false);
+        }
+    };
+
+    return (
+        <button className="lc-btn lc-btn--prim" onClick={onClick} disabled={busy || !drawNo}>
+            {busy ? '저장 중...' : `이대로 ${mode.sets}세트 구매했음`}
+        </button>
+    );
+}