settings: move dues config (Stripe + payment links) into its own Dues tab

The Stripe recurring-dues panel and the external payment-links panel were
rendered below the settings tab bar (outside SettingsClient), so they
floated under every tab. Add a Dues tab (Space / Integrations / Dues /
Webhooks) and render both panels there as standard tab cards. UI only.

app/(app)/settings/page.tsx

@@ -1,7 +1,5 @@
 import { createClient } from '@/lib/supabase/server'
 import SettingsClient from './settings-client'
-import { StripeBillingPanel } from '@/components/settings/stripe-billing-panel'
-import { DuesPaymentMethodsPanel } from '@/components/settings/dues-payment-methods-panel'
 import { redirect } from 'next/navigation'
 
 export default async function SettingsPage() {
@@ -27,15 +25,11 @@ export default async function SettingsPage() {
     .from('integrations').select('*').eq('space_id', member.space_id)
 
   return (
-    <>
-      <SettingsClient
-        space={space}
-        isAdmin={isAdmin}
-        integrations={integrations ?? []}
-        currentRole={member.role}
-      />
-      <StripeBillingPanel spaceId={member.space_id} />
-      <DuesPaymentMethodsPanel />
-    </>
+    <SettingsClient
+      space={space}
+      isAdmin={isAdmin}
+      integrations={integrations ?? []}
+      currentRole={member.role}
+    />
   )
 }