Fix NoExtraLayerCharge persistence, appointment reminders, coat notes display, scroll restoration, and invoice Send dead-button

- Appointment reminders: add AppointmentReminderBackgroundService (60s poll), ReminderSentAt
  dedup stamp, NotifyAppointmentReminderAsync sends both customer email and creator staff email;
  AppointmentReminderStaff notification type + default template added; DateTime.Now used instead
  of UtcNow to match locally-stored ScheduledStartTime; ToLocalTime() double-conversion removed

- NoExtraLayerCharge not persisted: flag existed on CreateQuoteItemCoatDto and was used by
  pricing engine but never written to JobItemCoat/QuoteItemCoat entities — every edit reset it
  to false and re-applied the extra layer charge; added column to both entities (migration
  AddNoExtraLayerChargeToCoats), both read DTOs, all 3 JobItemAssemblyService overloads,
  JobItemCoatSeed inner class, and existingItemsData JSON in all 5 wizard views; fixed JS
  template path that hard-coded noExtraLayerCharge: false

- Coat notes not visible: notes were rendered in desktop job details but missing from the wizard
  item card summary and the mobile card view; both fixed

- Scroll position lost on item save: sessionStorage save/restore added to item-wizard.js owner
  form submit handler; path-keyed so cross-page navigation does not restore stale position;
  requestAnimationFrame used for reliable mobile scroll restoration

- Invoice Send dead button: #sendChannelModal was gated inside @if (isDraft) but the button
  targeting it fires for Sent/Overdue invoices too when customer has both email and SMS; modal
  moved outside the Draft guard

- InitialCreate migration added for fresh database installs; Baseline migration guarded with
  IF OBJECT_ID check so it no-ops on fresh DBs; Razor scoping bug fixed in Customers/Index.cshtml

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

src/PowderCoating.Infrastructure/Migrations/20260316155002_Baseline.cs

@@ -11,26 +11,20 @@ namespace PowderCoating.Infrastructure.Migrations
         /// <inheritdoc />
         protected override void Up(MigrationBuilder migrationBuilder)
         {
-            migrationBuilder.UpdateData(
-                table: "PricingTiers",
-                keyColumn: "Id",
-                keyValue: 1,
-                column: "CreatedAt",
-                value: new DateTime(2026, 3, 16, 15, 49, 58, 737, DateTimeKind.Utc).AddTicks(7851));
-
-            migrationBuilder.UpdateData(
-                table: "PricingTiers",
-                keyColumn: "Id",
-                keyValue: 2,
-                column: "CreatedAt",
-                value: new DateTime(2026, 3, 16, 15, 49, 58, 737, DateTimeKind.Utc).AddTicks(7856));
-
-            migrationBuilder.UpdateData(
-                table: "PricingTiers",
-                keyColumn: "Id",
-                keyValue: 3,
-                column: "CreatedAt",
-                value: new DateTime(2026, 3, 16, 15, 49, 58, 737, DateTimeKind.Utc).AddTicks(7858));
+            // These UpdateData calls were generated from an existing live database.
+            // On a fresh install the PricingTiers table and its seed rows may not exist yet
+            // (seeding is manual via Platform Management → Seed Data), so guard each update.
+            migrationBuilder.Sql(@"
+                IF OBJECT_ID(N'[PricingTiers]', N'U') IS NOT NULL
+                BEGIN
+                    IF EXISTS (SELECT 1 FROM [PricingTiers] WHERE [Id] = 1)
+                        UPDATE [PricingTiers] SET [CreatedAt] = '2026-03-16T15:49:58.7377851Z' WHERE [Id] = 1;
+                    IF EXISTS (SELECT 1 FROM [PricingTiers] WHERE [Id] = 2)
+                        UPDATE [PricingTiers] SET [CreatedAt] = '2026-03-16T15:49:58.7377856Z' WHERE [Id] = 2;
+                    IF EXISTS (SELECT 1 FROM [PricingTiers] WHERE [Id] = 3)
+                        UPDATE [PricingTiers] SET [CreatedAt] = '2026-03-16T15:49:58.7377858Z' WHERE [Id] = 3;
+                END
+            ");
         }
 
         /// <inheritdoc />