refactor: remove stock-transaction service methods, endpoints, and DTOs

No job workflow ever called these (receive/use/adjust/scrap/recalculate)
- inventory quantity tracking is being removed per
docs/superpowers/specs/2026-08-01-remove-inventory-quantity-tracking-design.md.

CutList.Web/DTOs/StockItemDtos.cs

@@ -8,7 +8,6 @@ public class StockItemDto
     public decimal LengthInches { get; set; }
     public string LengthFormatted { get; set; } = string.Empty;
     public string? Name { get; set; }
-    public int QuantityOnHand { get; set; }
     public string? Notes { get; set; }
     public bool IsActive { get; set; }
 }
@@ -18,7 +17,6 @@ public class CreateStockItemDto
     public int MaterialId { get; set; }
     public string Length { get; set; } = string.Empty;
     public string? Name { get; set; }
-    public int QuantityOnHand { get; set; }
     public string? Notes { get; set; }
 }
 
@@ -28,40 +26,3 @@ public class UpdateStockItemDto
     public string? Name { get; set; }
     public string? Notes { get; set; }
 }
-
-public class StockTransactionDto
-{
-    public int Id { get; set; }
-    public int StockItemId { get; set; }
-    public int Quantity { get; set; }
-    public string Type { get; set; } = string.Empty;
-    public int? JobId { get; set; }
-    public string? JobNumber { get; set; }
-    public string? Notes { get; set; }
-    public DateTime CreatedAt { get; set; }
-}
-
-public class AddStockDto
-{
-    public int Quantity { get; set; }
-    public string? Notes { get; set; }
-}
-
-public class UseStockDto
-{
-    public int Quantity { get; set; }
-    public int? JobId { get; set; }
-    public string? Notes { get; set; }
-}
-
-public class AdjustStockDto
-{
-    public int NewQuantity { get; set; }
-    public string? Notes { get; set; }
-}
-
-public class ScrapStockDto
-{
-    public int Quantity { get; set; }
-    public string? Notes { get; set; }
-}