feat: add unit tests for featured listings, neighborhood scores + price history chart

- Add unit tests for FeatureListingHandler (6 tests) and ActivateFeaturedListingHandler (6 tests)
- Add unit tests for NeighborhoodScoreServiceImpl (5 tests) and GetNeighborhoodScoreHandler (2 tests)
- Add PriceHistoryChart component with recharts LineChart for listing detail page
- Wire up price history API client and integrate chart into listing detail view

Co-Authored-By: Paperclip <noreply@paperclip.ing>

apps/web/components/listings/price-history-chart.tsx

@@ -0,0 +1,73 @@
+'use client';
+
+import {
+  LineChart,
+  Line,
+  XAxis,
+  YAxis,
+  CartesianGrid,
+  Tooltip,
+  ResponsiveContainer,
+} from 'recharts';
+
+import type { PriceHistoryItem } from '@/lib/listings-api';
+
+interface PriceHistoryChartProps {
+  data: PriceHistoryItem[];
+  height?: number;
+}
+
+function priceToMillions(priceStr: string): number {
+  return Math.round(Number(priceStr) / 1_000_000);
+}
+
+function formatMillions(value: number): string {
+  if (value >= 1000) return `${(value / 1000).toFixed(1)} tỷ`;
+  return `${value} tr`;
+}
+
+export function PriceHistoryChart({ data, height = 280 }: PriceHistoryChartProps) {
+  if (data.length === 0) return null;
+
+  const chartData = [...data]
+    .sort((a, b) => new Date(a.changedAt).getTime() - new Date(b.changedAt).getTime())
+    .map((item) => ({
+      date: new Date(item.changedAt).toLocaleDateString('vi-VN', {
+        day: '2-digit',
+        month: '2-digit',
+        year: 'numeric',
+      }),
+      price: priceToMillions(item.newPrice),
+    }));
+
+  return (
+    <ResponsiveContainer width="100%" height={height}>
+      <LineChart data={chartData} margin={{ top: 5, right: 20, left: 0, bottom: 5 }}>
+        <CartesianGrid strokeDasharray="3 3" className="stroke-muted" />
+        <XAxis dataKey="date" tick={{ fontSize: 11 }} className="fill-muted-foreground" />
+        <YAxis
+          tick={{ fontSize: 11 }}
+          className="fill-muted-foreground"
+          tickFormatter={(v: number) => formatMillions(v)}
+        />
+        <Tooltip
+          contentStyle={{
+            backgroundColor: 'hsl(var(--card))',
+            border: '1px solid hsl(var(--border))',
+            borderRadius: '0.5rem',
+            fontSize: '0.875rem',
+          }}
+          formatter={(value) => [formatMillions(Number(value)), 'Giá']}
+        />
+        <Line
+          type="monotone"
+          dataKey="price"
+          stroke="hsl(var(--primary))"
+          strokeWidth={2}
+          dot={{ r: 4 }}
+          activeDot={{ r: 6 }}
+        />
+      </LineChart>
+    </ResponsiveContainer>
+  );
+}