feat(review): #90 wood primary category + derived thickness band

backend/slabs.py

@@ -13,6 +13,7 @@ from fastapi import APIRouter
 from fastapi.responses import JSONResponse, Response
 
 from .db import get_connection
+from .thickness_band import load_thickness_terms, resolve_thickness_band_id
 
 router = APIRouter(prefix="/api/v1/slabs")
 
@@ -133,6 +134,12 @@ async def create_slab(payload: Dict[str, Any]) -> Dict[str, Any]:
     conn = get_connection()
     if payload["sku"] is not None and _sku_taken(conn, payload["sku"]):
         return _err("duplicate_sku", "SKU already exists", {"sku": payload["sku"]}, status=409)
+    # METADATA-15 / QUALITY-95: the thickness band is derived, never owner-chosen.
+    # Resolve it from the measured thickness against the live synced Woo bands and
+    # overwrite whatever the client sent (the UI has no band control).
+    band = resolve_thickness_band_id(payload.get("thickness_in"), load_thickness_terms(conn))
+    if band is not None:
+        payload = {**payload, "thickness_term_id": band}
     now = _now_iso()
     data = _encode(payload)
     allowed_cols = [f for f in ALLOWED_FIELDS if f in data]
@@ -203,6 +210,10 @@ async def update_slab(id: str, payload: Dict[str, Any]) -> Dict[str, Any]:
                     live = [val]  # single-id field: just show what was submitted
                 return _err("stale_field", f"{field} not in current taxonomy",
                             {"field": field, "submitted": val, "current_options": live}, status=422)
+    eff_thickness = payload.get("thickness_in", current["thickness_in"])
+    band = resolve_thickness_band_id(eff_thickness, load_thickness_terms(conn))
+    if band is not None:
+        payload = {**payload, "thickness_term_id": band}
     data = _encode(payload)
     cols = [f for f in ALLOWED_UPDATE_FIELDS if f in data]
     if not cols: