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.

sql/migration.sql

@@ -164,14 +164,12 @@ CREATE TABLE category_attributes (
     CONSTRAINT uq_category_attribute UNIQUE (category_id, attribute_definition_id)
 );
 
--- ---------- MATERIALS (GLOBAL catalog entities — v2.5) ----------
--- category_id is NULLABLE and DERIVED automatically from the first linked
--- supplier (supplier_materials insert, first-link-wins). name is GLOBALLY
+-- ---------- MATERIALS (GLOBAL catalog entities — v2.6/v2.7) ----------
+-- Materials are global, category-free entities. name is GLOBALLY
 -- unique (uq_material_name). topic is a legacy display column no longer
 -- written by the app.
 CREATE TABLE materials (
     id                UUID            NOT NULL DEFAULT gen_random_uuid() PRIMARY KEY,
-    category_id       UUID            REFERENCES material_categories(id) ON DELETE RESTRICT,
     name              TEXT            NOT NULL,
     topic             TEXT,           -- LEGACY display column
     canonical_unit_id INTEGER         NOT NULL REFERENCES units(id) ON DELETE RESTRICT,
@@ -585,24 +583,6 @@ CREATE TRIGGER trg_quote_attachments_updated_at
 -- AUTOMATION TRIGGERS (v2.5 + v2.6)
 -- ============================================================================
 
--- Derive materials.category_id from the FIRST linked supplier (first-link-wins).
--- Idempotent: only touches rows where category_id IS NULL.
-CREATE OR REPLACE FUNCTION fn_derive_material_category()
-RETURNS TRIGGER AS $$
-BEGIN
-    UPDATE materials
-    SET category_id = (SELECT category_id FROM suppliers WHERE id = NEW.supplier_id),
-        updated_at  = now()
-    WHERE id = NEW.material_id
-      AND category_id IS NULL;
-    RETURN NEW;
-END;
-$$ LANGUAGE plpgsql;
-
-CREATE TRIGGER trg_supplier_materials_derive_category
-    AFTER INSERT ON supplier_materials
-    FOR EACH ROW EXECUTE FUNCTION fn_derive_material_category();
-
 -- Sync supplier_materials.last_quoted_price / last_quoted_at when an item
 -- decision becomes 'chosen' (INSERT or UPDATE — the accept-quote flow
 -- inserts decisions directly as 'chosen').