Fix pricing consistency across Quote → Job → Invoice; add stage-flow tests

- Store complete PricingBreakdownJson snapshot on Job at every save point so
  the Details page reads stored data rather than re-running the pricing engine
- Add 7 missing fields to Quote entity (FacilityOverheadCost, tier/quote discounts,
  SubtotalAfterDiscount) and persist them via ApplyPricingSnapshot
- Fix OvenCostId-as-rate bug in JobsController (FK was passed as decimal $/hr)
- Fix hardcoded LaborCost * 0.4 multiplier in two JobItemAssemblyService overloads
- Fix FacilityOverheadCost dropped from invoices in both quote and direct-job paths
- Fix RushFee missing from direct-job invoices (read from PricingBreakdownJson)
- Fix Notes and CatalogItemId not copied to InvoiceItem
- Add 14 unit tests in PricingStageFlowTests covering all three pricing stages

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

src/PowderCoating.Application/Services/JobItemAssemblyService.cs

@@ -27,7 +27,7 @@ public class JobItemAssemblyService : IJobItemAssemblyService
                 PowderCostOverride = source.PowderCostOverride,
                 UnitPrice = pricing.UnitPrice,
                 TotalPrice = pricing.TotalPrice,
-                LaborCost = pricing.TotalPrice * 0.4m,
+                LaborCost = pricing.LaborCost,
                 RequiresSandblasting = source.RequiresSandblasting,
                 RequiresMasking = source.RequiresMasking,
                 EstimatedMinutes = source.EstimatedMinutes,
@@ -113,7 +113,7 @@ public class JobItemAssemblyService : IJobItemAssemblyService
                 PowderCostOverride = source.PowderCostOverride,
                 UnitPrice = source.UnitPrice,
                 TotalPrice = source.TotalPrice,
-                LaborCost = source.TotalPrice * 0.4m,
+                LaborCost = source.ItemLaborCost,
                 RequiresSandblasting = source.RequiresSandblasting,
                 RequiresMasking = source.RequiresMasking,
                 EstimatedMinutes = source.EstimatedMinutes,