fix: add Upload button to header to open data source modal

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

App.tsx

@@ -701,6 +701,15 @@ const App: React.FC = () => {
           </div>
 
           <div className="flex items-center gap-3 md:gap-6">
+            {/* Data Source Settings */}
+            <button
+              onClick={() => setIsDataModalOpen(true)}
+              className="flex items-center gap-2 px-3 py-1.5 md:px-4 md:py-2 rounded-xl text-sm font-black uppercase tracking-widest transition-all bg-slate-900 text-slate-300 border border-border hover:border-emerald-500/50 hover:text-white shadow-lg active:scale-95"
+              title="Upload Data"
+            >
+              <UploadIcon />
+              <span className="hidden sm:inline">Upload</span>
+            </button>
             {/* Force Sync Action */}
             <button
               onClick={() => { handleDataFetch(); handleAdsFetch(); handleTrafficFetch(); handleVendorStockFetch(); handleBuyBoxFetch(); }}