Refactor: extract shared helpers, fix field drift, add assembly services

- IJobItemAssemblyService / IQuotePricingAssemblyService: centralize job item
  and quote pricing construction that was duplicated across create, rework copy,
  and quote-to-job conversion paths
- BlobFileHelper: single ValidateUpload/GetContentType/SanitizeFileName used by
  6 blob services (JobPhoto, QuotePhoto, ProfilePhoto, CompanyLogo, Equipment,
  Catalog) and BillsController + ExpensesController, removing 8 private copies
- PagedResult<T>.From(): static factory eliminates 6-line boilerplate in 11
  controllers (Appointments, Customers, Equipment, Inventory, Invoices, Jobs,
  Maintenance, CompanyUsers, PlatformUsers, Quotes, Vendors)
- AccountingDropdownHelper: single LoadAsync() call replaces duplicate
  vendor/account/job queries in BillsController and ExpensesController
- JobTemplateItem: add IsSalesItem + Sku fields with migration; propagate
  through JobTemplatesController snapshot copy and GetTemplatesJson projection,
  and JobsController template-application path
- Test assertions updated for standardized BlobFileHelper error messages

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

src/PowderCoating.Web/Helpers/AccountingDropdownHelper.cs

@@ -0,0 +1,99 @@
+using Microsoft.AspNetCore.Mvc.Rendering;
+using PowderCoating.Core.Enums;
+using PowderCoating.Core.Interfaces;
+
+namespace PowderCoating.Web.Helpers;
+
+/// <summary>
+/// Centralizes the repeated DB queries and SelectListItem projections used by the accounting
+/// controllers (Bills, Expenses). Each controller assigns only the properties it needs to ViewBag,
+/// so the naming mismatch between controllers (BankAccounts vs PaymentAccounts) is harmless.
+/// </summary>
+internal static class AccountingDropdownHelper
+{
+    /// <summary>
+    /// Loads vendors, accounts, payment methods, and active jobs in a single call.
+    /// Returns pre-projected SelectListItem collections so controllers avoid duplicating the
+    /// LINQ-to-SelectListItem transform.
+    /// </summary>
+    internal static async Task<AccountingDropdowns> LoadAsync(IUnitOfWork unitOfWork)
+    {
+        var vendors = await unitOfWork.Vendors.FindAsync(v => v.IsActive);
+        var allAccounts = await unitOfWork.Accounts.FindAsync(a => a.IsActive);
+        var jobs = await unitOfWork.Jobs.FindAsync(j =>
+            j.JobStatus.StatusCode != "COMPLETED" &&
+            j.JobStatus.StatusCode != "CANCELLED" &&
+            j.JobStatus.StatusCode != "DELIVERED");
+
+        var accountLabel = (Core.Entities.Account a) => $"{a.AccountNumber} – {a.Name}";
+
+        return new AccountingDropdowns
+        {
+            Vendors = vendors
+                .OrderBy(v => v.CompanyName)
+                .Select(v => new SelectListItem(v.CompanyName, v.Id.ToString()))
+                .ToList(),
+
+            ExpenseAccounts = allAccounts
+                .Where(a => a.AccountType == AccountType.Expense ||
+                            a.AccountType == AccountType.CostOfGoods)
+                .OrderBy(a => a.AccountNumber)
+                .Select(a => new SelectListItem(accountLabel(a), a.Id.ToString()))
+                .ToList(),
+
+            ExpenseAndAssetAccounts = allAccounts
+                .Where(a => a.AccountType == AccountType.Expense ||
+                            a.AccountType == AccountType.CostOfGoods ||
+                            a.AccountType == AccountType.Asset)
+                .OrderBy(a => a.AccountNumber)
+                .Select(a => new SelectListItem(accountLabel(a), a.Id.ToString()))
+                .ToList(),
+
+            ApAccounts = allAccounts
+                .Where(a => a.AccountSubType == AccountSubType.AccountsPayable)
+                .OrderBy(a => a.AccountNumber)
+                .Select(a => new SelectListItem(accountLabel(a), a.Id.ToString()))
+                .ToList(),
+
+            BankAccounts = allAccounts
+                .Where(a => a.AccountSubType == AccountSubType.Cash ||
+                            a.AccountSubType == AccountSubType.Checking ||
+                            a.AccountSubType == AccountSubType.Savings ||
+                            a.AccountSubType == AccountSubType.CreditCard)
+                .OrderBy(a => a.AccountNumber)
+                .Select(a => new SelectListItem(accountLabel(a), a.Id.ToString()))
+                .ToList(),
+
+            PaymentMethods = Enum.GetValues<PaymentMethod>()
+                .Select(m => new SelectListItem(m.ToString(), ((int)m).ToString()))
+                .ToList(),
+
+            ActiveJobs = jobs
+                .OrderBy(j => j.JobNumber)
+                .Select(j => new SelectListItem(
+                    $"{j.JobNumber} – {j.Description ?? "No description"}",
+                    j.Id.ToString()))
+                .ToList()
+        };
+    }
+}
+
+internal sealed class AccountingDropdowns
+{
+    public IReadOnlyList<SelectListItem> Vendors { get; init; } = [];
+
+    /// <summary>Expense + Cost of Goods accounts (used by Expenses controller).</summary>
+    public IReadOnlyList<SelectListItem> ExpenseAccounts { get; init; } = [];
+
+    /// <summary>Expense + Cost of Goods + Asset accounts (used by Bills controller).</summary>
+    public IReadOnlyList<SelectListItem> ExpenseAndAssetAccounts { get; init; } = [];
+
+    /// <summary>Accounts Payable accounts (used by Bills controller).</summary>
+    public IReadOnlyList<SelectListItem> ApAccounts { get; init; } = [];
+
+    /// <summary>Cash, Checking, Savings, and Credit Card accounts.</summary>
+    public IReadOnlyList<SelectListItem> BankAccounts { get; init; } = [];
+
+    public IReadOnlyList<SelectListItem> PaymentMethods { get; init; } = [];
+    public IReadOnlyList<SelectListItem> ActiveJobs { get; init; } = [];
+}