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.Application/Services/JobItemAssemblyService.cs

@@ -85,7 +85,8 @@ public class JobItemAssemblyService : IJobItemAssemblyService
                     TransferEfficiency = c.TransferEfficiency,
                     PowderCostPerLb = c.PowderCostPerLb,
                     PowderToOrder = CalculatePowderToOrder(c.PowderToOrder, source.SurfaceAreaSqFt, source.Quantity, c.CoverageSqFtPerLb, c.TransferEfficiency),
-                    Notes = c.Notes
+                    Notes = c.Notes,
+                    NoExtraLayerCharge = c.NoExtraLayerCharge
                 },
                 jobItemId,
                 companyId,
@@ -192,7 +193,8 @@ public class JobItemAssemblyService : IJobItemAssemblyService
                         TransferEfficiency = c.TransferEfficiency,
                         PowderCostPerLb = c.PowderCostPerLb,
                         PowderToOrder = CalculatePowderToOrder(c.PowderToOrder, source.SurfaceAreaSqFt, source.Quantity, c.CoverageSqFtPerLb, c.TransferEfficiency),
-                        Notes = c.Notes
+                        Notes = c.Notes,
+                        NoExtraLayerCharge = c.NoExtraLayerCharge
                     },
                     jobItemId,
                     companyId,
@@ -289,7 +291,8 @@ public class JobItemAssemblyService : IJobItemAssemblyService
                     TransferEfficiency = c.TransferEfficiency,
                     PowderCostPerLb = c.PowderCostPerLb,
                     PowderToOrder = c.PowderToOrder,
-                    Notes = c.Notes
+                    Notes = c.Notes,
+                    NoExtraLayerCharge = c.NoExtraLayerCharge
                 },
                 jobItemId,
                 companyId,
@@ -375,6 +378,7 @@ public class JobItemAssemblyService : IJobItemAssemblyService
             PowderCostPerLb = seed.PowderCostPerLb,
             PowderToOrder = seed.PowderToOrder,
             Notes = seed.Notes,
+            NoExtraLayerCharge = seed.NoExtraLayerCharge,
             CompanyId = companyId,
             CreatedAt = createdAtUtc
         };
@@ -493,6 +497,7 @@ public class JobItemAssemblyService : IJobItemAssemblyService
         public decimal? PowderCostPerLb { get; init; }
         public decimal? PowderToOrder { get; init; }
         public string? Notes { get; init; }
+        public bool NoExtraLayerCharge { get; init; }
     }
 
     /// <summary>Intermediate value object for prep service creation — see <see cref="JobItemSeed"/> for rationale.</summary>