feat: Sync PANEU inventory from Dropbox

- Add new API endpoint for PANEU stock from Dropbox
- Update handleVendorStockFetch to use new endpoint
- Configure Vite proxy for local development

api/fetch-paneu-stock.ts

@@ -0,0 +1,39 @@
+import type { VercelRequest, VercelResponse } from '@vercel/node';
+
+// PANEU Stock from Dropbox (using dl=1 for direct download)
+const PANEU_STOCK_DROPBOX_URL = "https://www.dropbox.com/scl/fi/xvsqi89mc8wk2i3jpndll/PANEU-Stock.xlsx?rlkey=djtbez2yi1sohjn203xnbjzl1&st=aogcoiw6&dl=1";
+
+export default async function handler(req: VercelRequest, res: VercelResponse) {
+    // CORS headers
+    res.setHeader('Access-Control-Allow-Origin', '*');
+    res.setHeader('Access-Control-Allow-Methods', 'GET, OPTIONS');
+    res.setHeader('Access-Control-Allow-Headers', 'Content-Type');
+
+    if (req.method === 'OPTIONS') {
+        return res.status(200).end();
+    }
+
+    try {
+        console.log('[fetch-paneu-stock] Fetching PANEU Stock from Dropbox...');
+        const response = await fetch(PANEU_STOCK_DROPBOX_URL, {
+            cache: 'no-store',
+            headers: {
+                'Pragma': 'no-cache',
+                'Cache-Control': 'no-cache'
+            }
+        });
+
+        if (!response.ok) {
+            throw new Error(`Dropbox responded with ${response.status}`);
+        }
+
+        const buffer = await response.arrayBuffer();
+        console.log('[fetch-paneu-stock] Successfully fetched PANEU Stock Excel, size:', buffer.byteLength);
+
+        res.setHeader('Content-Type', 'application/vnd.openxmlformats-officedocument.spreadsheetml.sheet');
+        res.status(200).send(Buffer.from(buffer));
+    } catch (error: any) {
+        console.error('[fetch-paneu-stock] Error:', error);
+        res.status(500).json({ error: error.message });
+    }
+}