feat: auto-load Traffic data from Dropbox on app startup

- api/fetch-traffic.ts: New endpoint to fetch Traffic Weekly.xlsx from Dropbox
- App.tsx: Added handleTrafficFetch function and auto-fetch on initialization

App.tsx

@@ -119,6 +119,25 @@ const App: React.FC = () => {
     }
   }, []);
 
+  const handleTrafficFetch = useCallback(async () => {
+    try {
+      console.log('[App] Fetching traffic from /api/fetch-traffic...');
+      const response = await fetch('/api/fetch-traffic');
+
+      if (!response.ok) {
+        throw new Error(`Failed to fetch Traffic: ${response.status} ${response.statusText}`);
+      }
+
+      const buffer = await response.arrayBuffer();
+      const data = await processTrafficExcel(buffer);
+
+      setTrafficData(data);
+      console.log('[App] Successfully loaded', data.length, 'traffic records');
+    } catch (error) {
+      console.error("Failed to fetch/parse Traffic", error);
+    }
+  }, []);
+
   const initializeData = (data: SalesRecord[]) => {
     setRawData(data);
     setFilters({
@@ -188,6 +207,10 @@ const App: React.FC = () => {
         console.log("Fetching fresh Ads from URL...");
         handleAdsFetch();
       }
+
+      // 1c. Always fetch Traffic data (no caching for now)
+      console.log("Fetching Traffic data...");
+      handleTrafficFetch();
     };
     initApp();
   }, [handleDataFetch]);