Add redirect for GET requests to /upload endpoint

Added a redirect handler for users who try to access /upload via GET
request instead of using the form POST. This prevents errors and guides
users to the proper upload form.

Changes:
- Added GET route for /upload that redirects to benefit forms page
- Added redirect_to_benefit_forms action in controller
- Shows info flash message directing users to the upload form

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

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

app/controllers/benefit_forms_controller.rb

@@ -16,6 +16,11 @@ class BenefitFormsController < ApplicationController
    end
   end
 
+  def redirect_to_benefit_forms
+    flash[:info] = "Please use the upload form below to upload files"
+    redirect_to user_benefit_forms_path(user_id: current_user.id)
+  end
+
   def upload
     file = params[:benefits][:upload]