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.Application/Interfaces/INotificationService.cs

@@ -58,7 +58,7 @@ public interface INotificationService
     /// Notify customer when an invoice has been sent.
     /// Optionally includes an online payment link in the email body.
     /// </summary>
-    Task NotifyInvoiceSentAsync(Invoice invoice, byte[]? pdfAttachment = null, string? pdfFilename = null, string? paymentUrl = null, string? overrideEmail = null);
+    Task NotifyInvoiceSentAsync(Invoice invoice, byte[]? pdfAttachment = null, string? pdfFilename = null, string? paymentUrl = null, string? overrideEmail = null, bool sendSms = false, string? viewUrl = null);
 
     /// <summary>
     /// Notify customer (internal) when a payment has been recorded on an invoice.