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/Kiosk/Welcome.cshtml

@@ -0,0 +1,32 @@
+@{
+    Layout = "~/Views/Shared/_KioskLayout.cshtml";
+    ViewData["Title"] = "Welcome";
+}
+
+<div id="kiosk-welcome-root"
+     data-company-id="@ViewBag.CompanyId"
+     class="kiosk-welcome-screen">
+
+    @if (!string.IsNullOrEmpty(ViewBag.CompanyLogoUrl as string))
+    {
+        <img src="@ViewBag.CompanyLogoUrl"
+             alt="@ViewBag.CompanyName"
+             class="kiosk-welcome-logo" />
+    }
+    else
+    {
+        <h1 class="kiosk-welcome-title">@ViewBag.CompanyName</h1>
+    }
+
+    <p class="kiosk-welcome-subtitle">Welcome! A staff member will start your intake shortly.</p>
+
+    <div class="kiosk-idle-indicator">
+        <span id="kiosk-conn-dot" style="display:inline-block;width:10px;height:10px;
+              border-radius:50%;background:#16a34a;margin-right:6px;transition:background 0.3s;"></span>
+        Ready
+    </div>
+</div>
+
+@section Scripts {
+    <script src="~/js/kiosk-welcome.js"></script>
+}