feat(organisation): add contact fields to model and API

Add contact_name, contact_email, phone, website columns. Wire the new
fields through the Organisation model, update request validation,
response resource, and the TypeScript Organisation interface. Needed by
the upcoming dashboard + form-builder binding registry.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

api/app/Models/Organisation.php

@@ -21,6 +21,10 @@ final class Organisation extends Model
     protected $fillable = [
         'name',
         'slug',
+        'contact_name',
+        'contact_email',
+        'phone',
+        'website',
         'billing_status',
         'settings',
         'email_logo_url',