fix: remove legacy admin payout process route and reorganize routes

- Remove legacy 'process' route from admin payouts (conflicted with Ruby's process method)
- Reorganize admin routes to logical position with proper section comment
- Simplify admin payout routes to only include actual functionality
- Update admin controller tests to test approval workflow instead of legacy routes
- Add proper test setup with banking info and onboarding completion
- Improve test coverage for admin authentication and payout approval

This resolves admin controller test failures and removes unnecessary legacy code
since the application is not yet published.

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

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

app/controllers/admin/payouts_controller.rb

@@ -60,12 +60,6 @@ class Admin::PayoutsController < ApplicationController
     end
   end
 
-  # Legacy method - redirect to new workflow
-  def process
-    @payout = Payout.find(params[:id])
-    redirect_to admin_payout_path(@payout), alert: "Use the new manual payout workflow."
-  end
-
   private
 
   def set_payout