feat: allow adding pantry items by text input with auto-ingredient creation

- backend: expose POST /api/ingredients on public router so frontend can create ingredients without admin token
- frontend/api: point listIngredients and createIngredient to /api/ingredients
- frontend/pantry: replace ingredient dropdown with searchable text input + fuzzy matching + auto-create

backend/app/api/ingredients.py

@@ -55,6 +55,26 @@ def get_ingredient(ingredient_id: UUID, db: Session = Depends(get_db)) -> Ingred
     return row
 
 
+@public_router.post("", response_model=IngredientRead, status_code=status.HTTP_201_CREATED)
+def create_ingredient_public(payload: IngredientCreate, db: Session = Depends(get_db)) -> Ingredient:
+    row = Ingredient(
+        name=payload.name,
+        name_lower=payload.name.lower(),
+        aliases=payload.aliases,
+        aisle=payload.aisle,
+        unit=payload.unit,
+        typical_price=payload.typical_price,
+    )
+    db.add(row)
+    try:
+        db.commit()
+    except IntegrityError:
+        db.rollback()
+        raise HTTPException(status_code=409, detail="ingredient name already exists")
+    db.refresh(row)
+    return row
+
+
 @admin_router.post("", response_model=IngredientRead, status_code=status.HTTP_201_CREATED)
 def create_ingredient(payload: IngredientCreate, db: Session = Depends(get_db)) -> Ingredient:
     row = Ingredient(