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/Modal.tsx

@@ -0,0 +1,38 @@
+'use client'
+
+import React from 'react'
+import { X } from 'lucide-react'
+
+export function Modal({
+  open,
+  onClose,
+  title,
+  children,
+  maxWidth = 'max-w-lg',
+}: {
+  open: boolean
+  onClose: () => void
+  title: string
+  children: React.ReactNode
+  maxWidth?: string
+}) {
+  if (!open) return null
+
+  return (
+    <div className="fixed inset-0 z-50 flex items-center justify-center p-4">
+      <div className="fixed inset-0 bg-black/40 backdrop-blur-sm" onClick={onClose} />
+      <div className={`relative bg-white rounded-2xl shadow-2xl w-full ${maxWidth} max-h-[90vh] overflow-y-auto`}>
+        <div className="flex items-center justify-between px-6 py-4 border-b border-slate-200">
+          <h2 className="text-lg font-semibold text-slate-900">{title}</h2>
+          <button
+            onClick={onClose}
+            className="p-1.5 rounded-lg text-slate-400 hover:text-slate-600 hover:bg-slate-100 transition-colors"
+          >
+            <X className="w-5 h-5" />
+          </button>
+        </div>
+        <div className="px-6 py-5">{children}</div>
+      </div>
+    </div>
+  )
+}