feat: replace Vendor tab with BSR tracker

api/fetch-bsr.ts

@@ -0,0 +1,27 @@
+import { promises as fs } from 'fs';
+import path from 'path';
+import type { VercelRequest, VercelResponse } from '@vercel/node';
+
+export default async function handler(req: VercelRequest, res: VercelResponse) {
+    try {
+        const filePath = path.join(process.cwd(), 'BSR.xlsx');
+
+        try {
+            await fs.access(filePath);
+        } catch {
+            return res.status(404).json({ error: 'BSR data file not found' });
+        }
+
+        const fileBuffer = await fs.readFile(filePath);
+
+        res.setHeader('Content-Type', 'application/vnd.openxmlformats-officedocument.spreadsheetml.sheet');
+        res.setHeader('Content-Disposition', 'attachment; filename="BSR.xlsx"');
+        res.setHeader('Cache-Control', 'public, max-age=3600');
+
+        // Convert Buffer to ArrayBuffer before sending for fetch compatibility on client
+        res.send(fileBuffer);
+    } catch (error) {
+        console.error('Error serving BSR Excel file:', error);
+        res.status(500).json({ error: 'Failed to serve BSR file' });
+    }
+}