Add smoke tests for UOM conversions and enhance frontend UOM management

- Implemented smoke tests for UOM directionality, ensuring conversions are one-directional and correctly validated.
- Added tests for receiving and selling items in different UOMs, verifying correct quantity handling and error responses.
- Created a UOM conversions panel in the frontend to allow users to manage UOM conversions for items.
- Introduced hooks for allowed UOMs to optimize fetching and caching of UOM data for document line forms.
- Developed utility functions for consistent UOM formatting and conversion handling across the application.

Backend/smoke/run_all.py

@@ -25,6 +25,11 @@ SCRIPTS = [
     ("M4b UOM conversion on stock inputs", "m4b_uom_conversion.py"),
     ("M5  terminal receipt + cost pool", "m5_receipt.py"),
     ("M6+M7 leftover / rework / cancel", "m6_m7_leftover_rework_cancel.py"),
+    # UOM engine. These run after the manufacturing scripts because they reuse the
+    # SMOKE-PRD warehouse m4 creates, and they drain it before seeding their own stock.
+    ("UOM conversion direction is enforced", "uom_direction.py"),
+    ("UOM non-base sales consume converted qty", "uom_sales_nonbase.py"),
+    ("UOM cross-unit GRN against a PO", "uom_grn_po_cross.py"),
 ]
 
 SUMMARY = re.compile(r"^(\S+): (\d+)/(\d+) assertions passed")