refactor: move studio to frontends workspace

- Move studio from root to frontends/studio/
- Add owner-tools frontend for live blog admin UI
- Add shared ui component library
- Set up npm workspaces for frontends
- Add enhanced code block extension for editor

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

frontends/studio/src/components/shared/EmptyState.tsx

@@ -0,0 +1,24 @@
+import type { ReactNode } from 'react'
+import type { IconComponent } from './Icons'
+
+interface EmptyStateProps {
+  Icon: IconComponent
+  title: string
+  description?: string
+  action?: ReactNode
+}
+
+export function EmptyState({ Icon, title, description, action }: EmptyStateProps) {
+  return (
+    <div className="card text-center py-12">
+      <div className="w-16 h-16 mx-auto mb-4 bg-border flex items-center justify-center">
+        <Icon className="text-muted text-2xl" />
+      </div>
+      <h3 className="text-sm font-medium text-text mb-1">{title}</h3>
+      {description && (
+        <p className="text-xs text-muted mb-4">{description}</p>
+      )}
+      {action}
+    </div>
+  )
+}