Add accounts UI with list, create, edit, detail tabs for all sub-entities

Accounts list with paginated table, search, sort. Account detail page with
tabs for members, payment methods, tax exemptions, and processor links.
All sub-entities have create/edit dialogs and delete actions. Forms use
shared Zod schemas via react-hook-form.

packages/admin/src/routes/_authenticated/accounts/$accountId.tsx

@@ -0,0 +1,71 @@
+import { createFileRoute, Outlet, Link, useParams } from '@tanstack/react-router'
+import { useQuery } from '@tanstack/react-query'
+import { accountDetailOptions } from '@/api/accounts'
+import { Skeleton } from '@/components/ui/skeleton'
+import { Badge } from '@/components/ui/badge'
+import { cn } from '@/lib/utils'
+
+export const Route = createFileRoute('/_authenticated/accounts/$accountId')({
+  component: AccountDetailLayout,
+})
+
+const tabs = [
+  { label: 'Overview', to: '/accounts/$accountId' },
+  { label: 'Members', to: '/accounts/$accountId/members' },
+  { label: 'Payment Methods', to: '/accounts/$accountId/payment-methods' },
+  { label: 'Tax Exemptions', to: '/accounts/$accountId/tax-exemptions' },
+  { label: 'Processor Links', to: '/accounts/$accountId/processor-links' },
+] as const
+
+function AccountDetailLayout() {
+  const { accountId } = useParams({ from: '/_authenticated/accounts/$accountId' })
+  const { data: account, isLoading } = useQuery(accountDetailOptions(accountId))
+
+  if (isLoading) {
+    return (
+      <div className="space-y-4">
+        <Skeleton className="h-8 w-64" />
+        <Skeleton className="h-4 w-96" />
+        <Skeleton className="h-10 w-full" />
+      </div>
+    )
+  }
+
+  if (!account) {
+    return <p className="text-muted-foreground">Account not found</p>
+  }
+
+  return (
+    <div className="space-y-6">
+      <div>
+        <div className="flex items-center gap-3">
+          <h1 className="text-2xl font-bold">{account.name}</h1>
+          <Badge variant="secondary">{account.billingMode}</Badge>
+        </div>
+        {account.email && <p className="text-muted-foreground">{account.email}</p>}
+      </div>
+
+      <nav className="flex gap-1 border-b">
+        {tabs.map((tab) => (
+          <Link
+            key={tab.to}
+            to={tab.to}
+            params={{ accountId }}
+            activeOptions={{ exact: tab.to === '/accounts/$accountId' }}
+            className={cn(
+              'px-4 py-2 text-sm font-medium border-b-2 -mb-px transition-colors',
+              'text-muted-foreground border-transparent hover:text-foreground hover:border-border',
+            )}
+            activeProps={{
+              className: 'text-foreground border-primary',
+            }}
+          >
+            {tab.label}
+          </Link>
+        ))}
+      </nav>
+
+      <Outlet />
+    </div>
+  )
+}