Add invoice SMS notifications and customer intake kiosk

Invoice SMS:
- Send Invoice modal now prompts Email/SMS/Both based on customer contact data
- New /invoice/{token} customer-facing view page with full line items and pay button
- PublicViewToken (permanent) added to Invoice; separate from expiring PaymentLinkToken
- InvoiceSent SMS default template added; customizable via Notification Templates settings
- {{viewUrl}} placeholder documented in template editor

Customer Intake Kiosk:
- Tablet kiosk flow: Contact → Job → Terms/Signature → Confirmation
- Remote link mode for off-site customers (lighter form, no signature)
- KioskHub (AllowAnonymous SignalR) for staff-to-tablet push without login
- Staff activates tablet via cookie; sends remote link manually
- Submitted sessions create Customer + Job automatically; fires in-app notification

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

src/PowderCoating.Web/Controllers/CompanySettingsController.cs

@@ -2685,6 +2685,7 @@ public class CompanySettingsController : Controller
         {
             list.Add(("{{invoiceTotal}}", "Invoice total amount (formatted as currency)"));
             list.Add(("{{invoiceDueDate}}", "Due date phrase, e.g. \" Due by January 1, 2026.\" — blank if no due date is set"));
+            list.Add(("{{viewUrl}}", "Permanent link for the customer to view the invoice online (used in SMS)"));
         }
 
         if (type == NotificationType.PaymentReceived)