Add Modify button handler to enable PO editing from dashboard

Problem:
- The "Modify" button in the Action Queue (Panel de Control) did nothing when clicked
- Previously removed handleModify function and onModify prop during earlier refactoring
- Users couldn't open the purchase order modal in edit mode from the dashboard

Solution:
- Added handleModify function that sets poModalMode to 'edit' before opening modal
- Updated handleViewDetails to explicitly set mode to 'view' for clarity
- Passed onModify handler to ActionQueueCard component

How it works:
- View button -> Opens modal in view mode (read-only)
- Modify button -> Opens modal in edit mode (editable fields)
- Both use the same PurchaseOrderDetailsModal component
- Modal's initialMode prop controls which mode is shown first

Now users can:
- Click "View Details" to see PO information
- Click "Modify" to edit priority, delivery date, notes, and product quantities
- See real-time updates as they edit quantities and prices

🤖 Generated with [Claude Code](https://claude.com/claude-code)

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

frontend/src/pages/app/DashboardPage.tsx

@@ -119,8 +119,16 @@ export function NewDashboardPage() {
   };
 
   const handleViewDetails = (actionId: string) => {
-    // Open modal to show PO details
+    // Open modal to show PO details in view mode
     setSelectedPOId(actionId);
+    setPOModalMode('view');
+    setIsPOModalOpen(true);
+  };
+
+  const handleModify = (actionId: string) => {
+    // Open modal to edit PO details
+    setSelectedPOId(actionId);
+    setPOModalMode('edit');
     setIsPOModalOpen(true);
   };
 
@@ -273,6 +281,7 @@ export function NewDashboardPage() {
               onApprove={handleApprove}
               onReject={handleReject}
               onViewDetails={handleViewDetails}
+              onModify={handleModify}
               tenantId={tenantId}
             />
           </div>