Add opt-in custom domains with automatic SSL

Customers can connect their own domain to a events page (storefront/event):
add a domain, point an A record (apex + www) to the app server, click Verify —
DNS is checked, then Ladill Domains' central SSL service issues + installs the
Let's Encrypt cert and calls back to flip it live. The custom domain then serves
the mapped page (host resolution on /). Feature-gated: only active when a Domains
SSL API key is set, so this deploy is inert until wired.

- custom_domains table + CustomDomain model
- CustomDomainService (DNS verify, request cert), DomainsSslClient, DnsResolver
- settings UI panel, signed SSL callback receiver, host resolution on /
- feature tests (DNS verify/fail, signed callback, ownership)

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

app/Http/Controllers/Qr/QrCodeController.php

@@ -226,6 +226,9 @@ class QrCodeController extends Controller
             'minTopup' => QrWallet::minTopupGhs(),
             'ladillWalletBalance' => $ladillWalletBalance,
             'topupUrl' => 'https://'.config('app.account_domain').'/wallet',
+            'customDomains' => \App\Models\CustomDomain::where('qr_code_id', $qrCode->id)->get(),
+            'customDomainsEnabled' => app(\App\Services\CustomDomain\CustomDomainService::class)->enabled(),
+            'customDomainServerIp' => config('customdomain.server_ip'),
         ]);
     }