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/MediaBrowser.tsx

@@ -259,7 +259,7 @@ export default function MediaBrowserPage() {
   }
 
   return (
-    <div className="p-6 space-y-5 max-w-screen-xl">
+    <div className="p-6 space-y-5">
       {/* Header */}
       <div className="flex items-center justify-between">
         <div>