Fix flash.now messages not displaying in benefit forms view

Changed flash message check to include both flash and flash.now since
error messages use flash.now when re-rendering without redirect.

This ensures validation error messages display immediately when users
upload invalid files.

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

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

app/views/benefit_forms/index.html.erb

@@ -1,9 +1,9 @@
 <div class="container-fluid">
   <!-- Flash Messages -->
-  <% if flash.any? %>
+  <% if flash.any? || flash.now.any? %>
     <div class="row mb-3">
       <div class="col-12">
-        <% flash.each do |name, msg| %>
+        <% (flash.to_hash.merge(flash.now.to_hash)).each do |name, msg| %>
           <%
             alert_class = case name.to_sym
             when :error, :alert then 'alert-danger'