fix(pantry): make public ingredient endpoint idempotent

Backend:
- POST /api/ingredients now checks name_lower and aliases before inserting
- Returns existing ingredient on 409 instead of throwing error

Frontend:
- Removed fragile 409-recovery logic from Pantry.tsx handleAdd
- Added aliases field to Ingredient type for case-insensitive matching

Fixes pantry add for ingredients like 'Carrots' whose canonical name is 'Carrot'

backend/app/api/ingredients.py

@@ -57,9 +57,24 @@ def get_ingredient(ingredient_id: UUID, db: Session = Depends(get_db)) -> Ingred
 
 @public_router.post("", response_model=IngredientRead, status_code=status.HTTP_201_CREATED)
 def create_ingredient_public(payload: IngredientCreate, db: Session = Depends(get_db)) -> Ingredient:
+    name_lower = payload.name.lower()
+    # idempotent: return existing if name or alias already known
+    existing = (
+        db.query(Ingredient)
+        .filter(
+            or_(
+                Ingredient.name_lower == name_lower,
+                Ingredient.aliases.any(payload.name.lower()),
+            )
+        )
+        .first()
+    )
+    if existing:
+        return existing
+
     row = Ingredient(
         name=payload.name,
-        name_lower=payload.name.lower(),
+        name_lower=name_lower,
         aliases=payload.aliases,
         aisle=payload.aisle,
         unit=payload.unit,
@@ -70,6 +85,19 @@ def create_ingredient_public(payload: IngredientCreate, db: Session = Depends(ge
         db.commit()
     except IntegrityError:
         db.rollback()
+        # race-window safety: re-check after rollback
+        existing = (
+            db.query(Ingredient)
+            .filter(
+                or_(
+                    Ingredient.name_lower == name_lower,
+                    Ingredient.aliases.any(payload.name.lower()),
+                )
+            )
+            .first()
+        )
+        if existing:
+            return existing
         raise HTTPException(status_code=409, detail="ingredient name already exists")
     db.refresh(row)
     return row

docs/ARCHITECTURE.md

@@ -299,6 +299,7 @@ Generate plan → Send proposal email (per-member tokens)
 | POST | `/api/pantry` | Add item to pantry |
 | DELETE | `/api/pantry/{id}` | Remove item from pantry |
 | POST | `/api/feedback` | Submit meal feedback |
+| POST | `/api/ingredients` | Create or resolve ingredient (public, idempotent) |
 | GET | `/api/recipes` | Search recipes |
 | POST | `/api/admin/scrape` | Trigger grocery scrape (admin) |
 | GET | `/api/admin/logs` | Get scraper logs |

frontend/src/pages/Pantry.tsx

@@ -31,10 +31,15 @@ export default function Pantry() {
     queryFn: () => mealPlannerApi.recipes.listIngredients().then(r => r.data),
   })
 
+  function _ingredientMatchesName(ing: Ingredient, search: string): boolean {
+    const s = search.toLowerCase()
+    return ing.name.toLowerCase() === s || (ing.aliases ?? []).some(a => a.toLowerCase() === s)
+  }
+
   /* fuzzy match existing ingredient */
   const matchedIngredient = ingredientName.trim().length > 0
     ? ingredients?.find(
-        ing => ing.name.toLowerCase() === ingredientName.trim().toLowerCase()
+        ing => _ingredientMatchesName(ing, ingredientName.trim())
       )
     : undefined
 
@@ -86,12 +91,8 @@ export default function Pantry() {
         ingredientId = created?.id
         // refresh ingredient list so next add sees it
         await queryClient.invalidateQueries({ queryKey: ['ingredients'] })
-      } catch (err: any) {
-        if (err?.response?.status === 409) {
-          showToast.error('Ingredient name already exists')
-        } else {
-          showToast.error('Failed to create ingredient')
-        }
+      } catch {
+        showToast.error('Failed to create ingredient')
         return
       }
     }

frontend/src/types/index.ts

@@ -100,6 +100,7 @@ export interface Ingredient {
   id: string
   name: string
   name_lower: string
+  aliases: string[]
   plural_name?: string
   aisle?: string
   typical_price?: number