Propagate catalog price to inventory and quote at current price

Quotes now reflect the current catalog price instead of a tenant's stale
typed-in cost, without disturbing accounting.

- InventoryItem gains CatalogReferencePrice + CatalogPriceUpdatedAt: the
  QUOTING price (current replacement cost), kept separate from UnitCost/
  AverageCost (the cost basis that drives valuation/COGS).
- The catalog sync (PowderCatalogUpsertService.PropagateToLinkedInventoryAsync,
  run at the end of every upsert) refreshes linked inventory items with the
  catalog's current price and product data (description, cure, SDS/TDS, color
  families, coverage, SG, transfer eff, requires-clear-coat). It NEVER touches
  cost, quantity, notes, image, location, or stock levels, and never nulls a
  tenant value with a catalog null. EF persists only actual changes.
- CatalogReferencePrice is also set at link time (catalog receive, incoming-
  from-catalog, identity match on create) so a freshly added powder quotes at
  the current price immediately.
- Pricing now uses CatalogReferencePrice ?? UnitCost: the quote/job powder
  pickers and PricingCalculationService (in-stock usage and powder-to-order
  billing). Falls back to UnitCost for non-catalog/manual powders, so nothing
  regresses. One current price for the whole quantity — no on-hand/to-order
  split. Per-coat snapshot still locks the price at quote creation.

Tests: propagation updates reference price + specs but not cost/qty/notes/
image, and skips a $0 catalog price. Full suite 276 green.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

src/PowderCoating.Infrastructure/Migrations/ApplicationDbContextModelSnapshot.cs

@@ -4075,6 +4075,12 @@ namespace PowderCoating.Infrastructure.Migrations
                     b.Property<decimal>("AverageCost")
                         .HasColumnType("decimal(18,2)");
 
+                    b.Property<DateTime?>("CatalogPriceUpdatedAt")
+                        .HasColumnType("datetime2");
+
+                    b.Property<decimal?>("CatalogReferencePrice")
+                        .HasColumnType("decimal(18,2)");
+
                     b.Property<string>("Category")
                         .IsRequired()
                         .HasColumnType("nvarchar(max)");
@@ -7235,7 +7241,7 @@ namespace PowderCoating.Infrastructure.Migrations
                         {
                             Id = 1,
                             CompanyId = 0,
-                            CreatedAt = new DateTime(2026, 6, 17, 16, 33, 6, 662, DateTimeKind.Utc).AddTicks(4251),
+                            CreatedAt = new DateTime(2026, 6, 17, 19, 26, 43, 161, DateTimeKind.Utc).AddTicks(2051),
                             Description = "Standard pricing for regular customers",
                             DiscountPercent = 0m,
                             IsActive = true,
@@ -7246,7 +7252,7 @@ namespace PowderCoating.Infrastructure.Migrations
                         {
                             Id = 2,
                             CompanyId = 0,
-                            CreatedAt = new DateTime(2026, 6, 17, 16, 33, 6, 662, DateTimeKind.Utc).AddTicks(4258),
+                            CreatedAt = new DateTime(2026, 6, 17, 19, 26, 43, 161, DateTimeKind.Utc).AddTicks(2056),
                             Description = "5% discount for preferred customers",
                             DiscountPercent = 5m,
                             IsActive = true,
@@ -7257,7 +7263,7 @@ namespace PowderCoating.Infrastructure.Migrations
                         {
                             Id = 3,
                             CompanyId = 0,
-                            CreatedAt = new DateTime(2026, 6, 17, 16, 33, 6, 662, DateTimeKind.Utc).AddTicks(4259),
+                            CreatedAt = new DateTime(2026, 6, 17, 19, 26, 43, 161, DateTimeKind.Utc).AddTicks(2057),
                             Description = "10% discount for premium customers",
                             DiscountPercent = 10m,
                             IsActive = true,