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/ui/src/Button.tsx

@@ -0,0 +1,64 @@
+import type { ButtonHTMLAttributes, AnchorHTMLAttributes, ReactNode } from 'react'
+import { Icons, type IconComponent } from './Icons'
+
+type ButtonVariant = 'primary' | 'secondary' | 'danger' | 'ghost' | 'accent'
+
+type ButtonBaseProps = {
+  variant?: ButtonVariant
+  loading?: boolean
+  Icon?: IconComponent
+  children: ReactNode
+}
+
+type ButtonAsButton = ButtonBaseProps & ButtonHTMLAttributes<HTMLButtonElement> & { href?: never }
+type ButtonAsLink = ButtonBaseProps & AnchorHTMLAttributes<HTMLAnchorElement> & { href: string }
+
+type ButtonProps = ButtonAsButton | ButtonAsLink
+
+const variantClasses: Record<ButtonVariant, string> = {
+  primary: 'btn-primary',
+  secondary: 'btn-secondary',
+  danger: 'btn-danger',
+  ghost: 'btn-ghost',
+  accent: 'btn-accent',
+}
+
+export function Button({
+  variant = 'secondary',
+  loading = false,
+  Icon,
+  children,
+  className = '',
+  ...props
+}: ButtonProps) {
+  const content = (
+    <>
+      {loading ? (
+        <Icons.Loader className="animate-spin text-xs" />
+      ) : Icon ? (
+        <Icon className="text-xs opacity-70" />
+      ) : null}
+      <span>{children}</span>
+    </>
+  )
+
+  if ('href' in props && props.href) {
+    const { href, ...linkProps } = props
+    return (
+      <a href={href} className={`${variantClasses[variant]} ${className}`} {...linkProps}>
+        {content}
+      </a>
+    )
+  }
+
+  const { disabled, ...buttonProps } = props as ButtonAsButton
+  return (
+    <button
+      className={`${variantClasses[variant]} ${className}`}
+      disabled={disabled || loading}
+      {...buttonProps}
+    >
+      {content}
+    </button>
+  )
+}