Refactor production and stock tests to remove UOM dependency

- Updated production.spec.ts, stock-adjustments.spec.ts, and stock-transfers.spec.ts to eliminate UOM references in API seeder and test cases.
- Adjusted ApiSeeder methods to remove UOM parameters from stock receiving and production template creation.
- Revised documentation to reflect changes in UOM handling, emphasizing that stock is counted in base UOM only.
- Introduced new enums for MeasureUnit and StageQtyUnit to clarify content size and stage input quantities.
- Implemented ItemContent service to validate and normalize content sizes.
- Updated smoke tests to validate production stage inputs expressed in content units, ensuring correct consumption calculations.
- Modified frontend UOM label handling to reflect the removal of per-line UOMs in document lines.

Backend/ERPCore/System/Errors/ErrorCodes.cs

@@ -56,6 +56,7 @@ public static class ErrorCodes
     public const string GraphDisconnected = "GRAPH_DISCONNECTED";
     public const string GraphInputSourceInvalid = "GRAPH_INPUT_SOURCE_INVALID";
     public const string TerminalOutputItemRequired = "TERMINAL_OUTPUT_ITEM_REQUIRED";
+    public const string WipUnitRequired = "WIP_UNIT_REQUIRED";
     public const string StageNotReady = "STAGE_NOT_READY";
     public const string StageNotInProgress = "STAGE_NOT_IN_PROGRESS";
     public const string StageNotDone = "STAGE_NOT_DONE";