feat(analytics): AVM v2 batch valuation, comparison, history + frontend upgrade

Add batch valuation (POST /analytics/valuation/batch, max 50 properties),
valuation comparison (POST /analytics/valuation/compare, 2-5 properties),
and history endpoint (GET /analytics/valuation/history/:propertyId) with
confidence explanation helper. Frontend: enhanced valuation form with project
autocomplete and deep analysis toggle, results with confidence badges and
price range visualization, comparables table, history chart, market context
card, and PDF export.

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

apps/web/components/valuation/export-pdf-button.tsx

@@ -0,0 +1,176 @@
+'use client';
+
+import { Download, Loader2 } from 'lucide-react';
+import { useCallback, useState } from 'react';
+import { Button } from '@/components/ui/button';
+
+interface ExportPdfButtonProps {
+  /** CSS selector for the DOM element to capture */
+  targetSelector: string;
+  /** Filename without extension */
+  filename?: string;
+}
+
+export function ExportPdfButton({
+  targetSelector,
+  filename = 'dinh-gia-bat-dong-san',
+}: ExportPdfButtonProps) {
+  const [isExporting, setIsExporting] = useState(false);
+
+  const handleExport = useCallback(async () => {
+    setIsExporting(true);
+    try {
+      const element = document.querySelector(targetSelector);
+      if (!element) {
+        console.error('Export target not found:', targetSelector);
+        return;
+      }
+
+      // Dynamic imports for client-only PDF libraries
+      const [html2canvasModule, jsPDFModule] = await Promise.all([
+        import('html2canvas'),
+        import('jspdf'),
+      ]);
+      const html2canvas = html2canvasModule.default;
+      const { jsPDF } = jsPDFModule;
+
+      const canvas = await html2canvas(element as HTMLElement, {
+        scale: 2,
+        useCORS: true,
+        logging: false,
+        backgroundColor: '#ffffff',
+      });
+
+      const imgData = canvas.toDataURL('image/png');
+      const imgWidth = canvas.width;
+      const imgHeight = canvas.height;
+
+      // A4 dimensions in mm
+      const pdfWidth = 210;
+      const pdfMargin = 10;
+      const contentWidth = pdfWidth - 2 * pdfMargin;
+      const contentHeight = (imgHeight / imgWidth) * contentWidth;
+
+      const pdf = new jsPDF({
+        orientation: contentHeight > 297 - 2 * pdfMargin ? 'portrait' : 'portrait',
+        unit: 'mm',
+        format: 'a4',
+      });
+
+      // Add header
+      pdf.setFontSize(16);
+      pdf.setTextColor(34, 139, 34); // Green
+      pdf.text('GoodGo — Báo cáo định giá', pdfMargin, pdfMargin + 5);
+      pdf.setFontSize(10);
+      pdf.setTextColor(128, 128, 128);
+      pdf.text(
+        `Ngày: ${new Date().toLocaleDateString('vi-VN')}`,
+        pdfMargin,
+        pdfMargin + 12,
+      );
+
+      const headerHeight = 20;
+      const availableHeight = 297 - 2 * pdfMargin - headerHeight;
+
+      if (contentHeight <= availableHeight) {
+        // Fits on one page
+        pdf.addImage(
+          imgData,
+          'PNG',
+          pdfMargin,
+          pdfMargin + headerHeight,
+          contentWidth,
+          contentHeight,
+        );
+      } else {
+        // Multi-page: split the image
+        let yOffset = 0;
+        let isFirstPage = true;
+
+        while (yOffset < contentHeight) {
+          if (!isFirstPage) {
+            pdf.addPage();
+          }
+
+          const pageContentHeight = isFirstPage
+            ? availableHeight
+            : 297 - 2 * pdfMargin;
+          const pageTopMargin = isFirstPage
+            ? pdfMargin + headerHeight
+            : pdfMargin;
+
+          // Calculate source rectangle in image coordinates
+          const srcY = (yOffset / contentHeight) * imgHeight;
+          const srcHeight = (pageContentHeight / contentHeight) * imgHeight;
+
+          // Create a temporary canvas for this page slice
+          const pageCanvas = document.createElement('canvas');
+          pageCanvas.width = imgWidth;
+          pageCanvas.height = Math.min(srcHeight, imgHeight - srcY);
+
+          const ctx = pageCanvas.getContext('2d');
+          if (ctx) {
+            ctx.drawImage(
+              canvas,
+              0,
+              srcY,
+              imgWidth,
+              pageCanvas.height,
+              0,
+              0,
+              imgWidth,
+              pageCanvas.height,
+            );
+          }
+
+          const pageImgData = pageCanvas.toDataURL('image/png');
+          const sliceHeight =
+            (pageCanvas.height / imgWidth) * contentWidth;
+
+          pdf.addImage(
+            pageImgData,
+            'PNG',
+            pdfMargin,
+            pageTopMargin,
+            contentWidth,
+            sliceHeight,
+          );
+
+          yOffset += pageContentHeight;
+          isFirstPage = false;
+        }
+      }
+
+      // Footer on last page
+      pdf.setFontSize(8);
+      pdf.setTextColor(180, 180, 180);
+      pdf.text(
+        'Được tạo bởi GoodGo AI Valuation — goodgo.vn',
+        pdfMargin,
+        297 - pdfMargin,
+      );
+
+      pdf.save(`${filename}.pdf`);
+    } catch (error) {
+      console.error('PDF export failed:', error);
+    } finally {
+      setIsExporting(false);
+    }
+  }, [targetSelector, filename]);
+
+  return (
+    <Button
+      variant="outline"
+      size="sm"
+      onClick={handleExport}
+      disabled={isExporting}
+    >
+      {isExporting ? (
+        <Loader2 className="mr-2 h-4 w-4 animate-spin" />
+      ) : (
+        <Download className="mr-2 h-4 w-4" />
+      )}
+      {isExporting ? 'Đang xuất...' : 'Xuất PDF'}
+    </Button>
+  );
+}