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/smoke/smoke_common.py

@@ -240,15 +240,16 @@ def seed_costed_stock(c, warehouse_id: int, lines, vendor_id: int | None = None)
     """
     Create on-hand at explicit unit costs via a direct GRN + confirm.
 
-    `lines` is an iterable of (item_id, uom_id, qty, unit_cost).
+    `lines` is an iterable of (item_id, qty, unit_cost). Quantities are counts of the item's
+    base UOM — document lines carry no unit of their own.
     """
     vendor_id = vendor_id or ensure_vendor(c)
     grn = c.post("/grns", {
         "vendorId": vendor_id,
         "warehouseId": warehouse_id,
         "lines": [
-            {"itemId": i, "uomId": u, "qty": q, "unitCost": cost, "discountPct": 0, "vatPct": 0}
-            for (i, u, q, cost) in lines
+            {"itemId": i, "qty": q, "unitCost": cost, "discountPct": 0, "vatPct": 0}
+            for (i, q, cost) in lines
         ],
     })
     if grn.status != 201: