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/ProductDetail.tsx

@@ -311,7 +311,7 @@ export default function ProductDetailPage() {
   if (!product) return <div className="p-8 text-red-500">Product not found</div>
 
   return (
-    <div className="p-8 max-w-4xl mx-auto">
+    <div className="p-8">
       {/* Back */}
       <Link to="/products" className="inline-flex items-center gap-1 text-sm text-content-secondary hover:text-content mb-4">
         <ArrowLeft size={15} /> Products