fix: full-width content area + auto-create MediaAssets on render complete

- Remove max-w-* constraints from all data/table pages so content fills available width after sidebar (Billing, MediaBrowser, OrderDetail, WorkerManagement, WorkerActivity, Materials, Tenants, AssetLibrary, NewProductOrder, ProductDetail)
- Narrow form/settings pages keep their max-width (NotificationSettings, Preferences, NewOrder, Notifications)
- render_order_line_task: create MediaAsset record on render success so results immediately appear in Media Browser without requiring the retroactive import button

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

frontend/src/pages/NewProductOrder.tsx

@@ -331,7 +331,7 @@ export default function NewProductOrderPage() {
   }
 
   return (
-    <div className="p-8 max-w-6xl mx-auto">
+    <div className="p-8">
       {/* Header */}
       <div className="flex items-center gap-4 mb-6">
         <Link to="/orders/new" className="btn-secondary"><ArrowLeft size={16} />Back</Link>