Add Custom Formula Item Templates with AI generation and wizard integration

Introduces per-company reusable NCalc2 pricing formula templates for complex
fabricated items (roof curbs, enclosures, welded frames). Templates support
two output modes — FixedRate (formula yields a dollar amount) and SurfaceAreaSqFt
(formula yields sq ft fed into the standard coating engine). Includes:

- CustomItemTemplate entity, migration (AddCustomItemTemplates), IUnitOfWork repo
- IsCustomFormulaItem / CustomItemTemplateId / FormulaFieldValuesJson flags on
  QuoteItem, JobItem, CreateQuoteItemDto; mapped in all 3 JobItemAssemblyService
  overloads and all existingItemsData JSON projections + pageMeta blocks
- ICustomFormulaAiService / CustomFormulaAiService: Claude-powered formula
  generator (natural language + optional diagram image) and NCalc2 evaluator
- CompanySettings CRUD endpoints: GetCustomItemTemplates, Create/Update/Delete,
  UploadTemplateDiagram, TemplateDiagram (blob serve), EvaluateFormula, GenerateFormulaFromAi
- Company Settings "Custom Formulas" tab + cfModal + company-settings-custom-formulas.js
- item-wizard.js: formula item type card, renderFormulaFields, wzFormulaRecalc
  (live evaluate via POST), collectStep2 formula branch, buildCardHtml / emitHiddenFields
- Formula badge in Quotes/Details and Jobs/Details; AI badge gap fixed in Jobs/Details
- Help article (CustomFormulaTemplates.cshtml), Help Index card, HelpController action,
  HelpKnowledgeBase entry; 225/225 unit tests passing

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

src/PowderCoating.Web/Program.cs

@@ -219,6 +219,7 @@ builder.Services.AddScoped<IOperationalReportService, OperationalReportService>(
 builder.Services.AddScoped<IAiHelpService, AiHelpService>();
 builder.Services.AddScoped<IAiCatalogPriceCheckService, AiCatalogPriceCheckService>();
 builder.Services.AddScoped<IInventoryAiLookupService, InventoryAiLookupService>();
+builder.Services.AddScoped<ICustomFormulaAiService, CustomFormulaAiService>();
 builder.Services.AddHttpClient();
 builder.Services.AddScoped<ICompanyLogoService, CompanyLogoService>();
 builder.Services.AddScoped<IEquipmentManualService, EquipmentManualService>();
@@ -292,6 +293,7 @@ cfg.AddProfile(new CatalogProfile());
         cfg.AddProfile(new AccountingProfile());
         cfg.AddProfile(new PurchaseOrderProfile());
         cfg.AddProfile(new PricingTierProfile());
+        cfg.AddProfile(new CustomItemTemplateProfile());
     }, loggerFactory);
     return config.CreateMapper();
 });