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/Views/Shared/_Layout.cshtml

@@ -1136,6 +1136,13 @@
                         <span>Daily Board</span>
                     </a>
                 }
+                @if (hasJobs)
+                {
+                    <a asp-controller="Kiosk" asp-action="Intakes" class="nav-link" data-nav="ops">
+                        <i class="bi bi-tablet"></i>
+                        <span>Intake Sessions</span>
+                    </a>
+                }
 
                 @* ── Billing & Payments ───────────────────────────────────── *@
                 @if (hasInvoices)
@@ -1492,6 +1499,7 @@
                                     <li><a class="dropdown-item" asp-controller="CompanyUsers" asp-action="Index"><i class="bi bi-people-fill me-2"></i>Manage Users</a></li>
                                     <li><a class="dropdown-item" asp-controller="PricingTiers" asp-action="Index"><i class="bi bi-tags me-2"></i>Pricing Tiers</a></li>
                                     <li><a class="dropdown-item" asp-controller="TaxRates" asp-action="Index"><i class="bi bi-percent me-2"></i>Tax Rates</a></li>
+                                    <li><a class="dropdown-item" asp-controller="Kiosk" asp-action="Activate"><i class="bi bi-tablet me-2"></i>Kiosk Setup</a></li>
                                 }
                                 <li><hr class="dropdown-divider"></li>
                                 @if (gearIsAdmin)