Remove max-width constraint from root layout

The root +layout.svelte had max-w-7xl and mx-auto which constrained
the entire app to 1280px centered. Removed to allow full-width layout
where sidebar extends to the left edge of the viewport.

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

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

apps/publisher-dashboard/src/routes/+layout.svelte

@@ -9,6 +9,4 @@ interface Props {
 let { children }: Props = $props();
 </script>
 
-<main class="mx-auto max-w-7xl p-4">
+{@render children()}
-  {@render children()}
-</main>