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

vite.config.ts

@@ -14,6 +14,12 @@ export default defineConfig(({ mode }) => {
           changeOrigin: true,
           rewrite: () => '',  // Replace entire path with empty string (target has full URL)
           followRedirects: true
+        },
+        '/api/fetch-paneu-stock': {
+          target: 'https://www.dropbox.com/scl/fi/xvsqi89mc8wk2i3jpndll/PANEU-Stock.xlsx?rlkey=djtbez2yi1sohjn203xnbjzl1&st=aogcoiw6&dl=1',
+          changeOrigin: true,
+          rewrite: () => '',
+          followRedirects: true
         }
       }
     },