Merge prod_v5 (catalog v2.7, warehouse locking, per-project accept) into integration

Conflict in init_db.py resolved keeping the audit_log table ensure
function (new-one) — prod_v5 predates it and its side was empty.
Both sides' SQL lands: audit_log table plus the category-free materials
model.

backend/tools/seed.py

@@ -261,9 +261,7 @@ async def run() -> None:
         material_by_name: dict[str, Material] = {}
         brand_material_by_material: dict[str, object] = {}
         for name, cat_slug, unit_code, brand_name in MATERIALS:
-            cat = await get_category(db, cat_slug)
             material = Material(
-                category_id=cat.id,
                 name=name,
                 canonical_unit_id=unit_ids[unit_code],
                 status="active",
@@ -289,8 +287,10 @@ async def run() -> None:
             await db.flush()
             suppliers.append(sup)
         # last-quoted prices: link each supplier to 2 materials of its category
+        sup_cat_slug = {name: cat_slug for name, cat_slug, *_ in SUPPLIERS}
         for sup in suppliers:
-            cat_materials = [m for m in material_by_name.values() if m.category_id == sup.category_id]
+            target_slug = sup_cat_slug.get(sup.name)
+            cat_materials = [material_by_name[mat_name] for mat_name, c_slug, *_ in MATERIALS if c_slug == target_slug]
             for m in cat_materials[:2]:
                 db.add(SupplierMaterial(
                     supplier_id=sup.id, material_id=m.id, is_active=True,