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/run_all.py

@@ -22,7 +22,7 @@ SCRIPTS = [
     ("M2  templates + graph validation", "m2_templates.py"),
     ("M3  run creation / board / quantities", "m3_runs.py"),
     ("M4  stage start / complete / approve / transfer", "m4_stage_actions.py"),
-    ("M4b UOM conversion on stock inputs", "m4b_uom_conversion.py"),
+    ("M4c content-unit stage inputs + fractional packs", "m4c_content_units.py"),
     ("M5  terminal receipt + cost pool", "m5_receipt.py"),
     ("M6+M7 leftover / rework / cancel", "m6_m7_leftover_rework_cancel.py"),
 ]