fix: enhance CSV import rate limiting and UI protection

- Reduce batch size from 3 to 2 expenses per batch for more conservative processing
- Increase delay between batches from 1.5s to 2s to prevent HTTP 429 errors
- Add isProcessingExpenses state to prevent multiple simultaneous imports
- Disable import buttons during expense processing for better UX
- Ensure processing state is always cleared in finally block

Resolves HTTP 429 rate limiting errors during bulk expense creation from CSV imports.

client/src/pages/DataImport.tsx

@@ -54,6 +54,7 @@ export default function DataImport() {
   const [etsyFile, setEtsyFile] = useState<File | null>(null);
   const [shippingFile, setShippingFile] = useState<File | null>(null);
   const [isLoading, setIsLoading] = useState(false);
+  const [isProcessingExpenses, setIsProcessingExpenses] = useState(false);
   const [results, setResults] = useState<ImportResults | null>(null);
   
   // PDF Import State
@@ -117,6 +118,8 @@ export default function DataImport() {
     etsyFees: EtsyFeeRecord[]
   ) => {
     try {
+      setIsProcessingExpenses(true);
+      
       // Get existing expenses to avoid duplicates
       const existingExpensesRes = await api.get('/expenses?limit=1000');
       const existingExpenses = existingExpensesRes.data.expenses || [];
@@ -180,9 +183,9 @@ export default function DataImport() {
         let created = 0;
         let skippedDuplicates = 0;
         
-        // Process expenses with rate limiting (conservative approach to avoid 429 errors)
+        // Process expenses with very conservative rate limiting to prevent 429 errors
-        const BATCH_SIZE = 3; // Reduced from 5 to be more conservative  
+        const BATCH_SIZE = 2; // Further reduced to 2 expenses per batch
-        const DELAY_MS = 1500; // Increased delay to 1.5 seconds
+        const DELAY_MS = 2000; // Increased to 2 seconds between batches
         const totalBatches = Math.ceil(expensesToCreate.length / BATCH_SIZE);
         
         console.log(`Creating ${expensesToCreate.length} expenses in ${totalBatches} batches to avoid rate limiting...`);
@@ -249,6 +252,8 @@ export default function DataImport() {
     } catch (error) {
       console.error('Error creating expenses:', error);
       toast.error('Failed to create expenses from CSV data');
+    } finally {
+      setIsProcessingExpenses(false);
     }
   };
 
@@ -838,10 +843,10 @@ export default function DataImport() {
             <div className="mt-6 flex gap-4">
               <button
                 onClick={processCsvFiles}
-                disabled={!etsyFile || isLoading}
+                disabled={!etsyFile || isLoading || isProcessingExpenses}
                 className="bg-blue-600 text-white px-6 py-2 rounded-lg hover:bg-blue-700 disabled:bg-gray-400"
               >
-                {isLoading ? 'Processing...' : 'Analyze Financial Data'}
+                {isLoading || isProcessingExpenses ? 'Processing...' : 'Analyze Financial Data'}
               </button>
             </div>
           </div>
@@ -973,7 +978,8 @@ export default function DataImport() {
               </div>
               <button
                 onClick={createOrdersFromCSV}
-                className="flex items-center gap-2 px-4 py-2 bg-blue-600 text-white rounded-lg hover:bg-blue-700 ml-4"
+                disabled={isProcessingExpenses}
+                className="flex items-center gap-2 px-4 py-2 bg-blue-600 text-white rounded-lg hover:bg-blue-700 disabled:bg-gray-400 ml-4"
               >
                 <Package className="w-4 h-4" />
                 Re-sync Orders