refactor(admin): split multi-tenant page.tsx into colocated components

Extract types, constants, helpers, and UI pieces (LoadingSkeleton,
EmptyState, StatCard, ComplianceRing, Modal, TenantCard,
CreateTenantModal, EditTenantModal, TenantDetailModal) into
_components/ and _types.ts to bring page.tsx from 1663 LOC to
432 LOC (under the 500 hard cap). Behavior preserved.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

admin-compliance/app/sdk/multi-tenant/_components/EmptyState.tsx

@@ -0,0 +1,26 @@
+'use client'
+
+import React from 'react'
+
+export function EmptyState({
+  icon,
+  title,
+  description,
+  action,
+}: {
+  icon: React.ReactNode
+  title: string
+  description: string
+  action?: React.ReactNode
+}) {
+  return (
+    <div className="text-center py-16">
+      <div className="w-16 h-16 mx-auto bg-indigo-50 rounded-full flex items-center justify-center mb-4">
+        {icon}
+      </div>
+      <h3 className="text-lg font-semibold text-slate-900">{title}</h3>
+      <p className="mt-2 text-sm text-slate-500 max-w-md mx-auto">{description}</p>
+      {action && <div className="mt-6">{action}</div>}
+    </div>
+  )
+}