feat(M2): Open Food Facts 采集导入 ETL

- adapters/openfoodfacts.py: OFF API 适配器(限速+User-Agent) + JSONL/.gz dump 读取
- etl/transform.py: 纯函数转换(GTIN 校验/净含量解析+归一/营养 per_100g 双能量/过敏原添加剂清洗/关键词分类映射)
- etl/load.py: psycopg upsert(product/food_detail/product_image) + product_source 字段级溯源
- jobs/seed_off.py: CLI(--barcodes API / --dump 文件 / --limit)
- 测试: 13 个离线 transform 单测(fixture) + 可跳过的 DB 集成测试
- 依赖: 增加 psycopg[binary]
- 实跑: 从 OFF API 拉 5 个真实条码入本地 postgres 验证通过
- docs/etl-openfoodfacts.md: 流程/运行/字段映射

Co-Authored-By: Devin AI <158243242+devin-ai-integration[bot]@users.noreply.github.com>

ingestion/tests/test_load_integration.py

@@ -0,0 +1,61 @@
+"""Integration test for the DB loader.
+
+Skipped automatically when no database is reachable (e.g. local runs without
+docker, or CI jobs without a postgres service). Requires migrations applied.
+"""
+
+from __future__ import annotations
+
+import json
+from pathlib import Path
+
+import pytest
+
+from opengoods.etl.load import default_dsn, ensure_source, load_record
+from opengoods.etl.transform import transform
+
+psycopg = pytest.importorskip("psycopg")
+
+FIXTURE = json.loads((Path(__file__).parent / "fixtures" / "off_product.json").read_text())
+
+
+@pytest.fixture()
+def conn():
+    try:
+        c = psycopg.connect(default_dsn(), connect_timeout=3)
+    except psycopg.OperationalError as exc:  # pragma: no cover - env dependent
+        pytest.skip(f"no database available: {exc}")
+    # ensure schema present
+    has_product = c.execute("SELECT to_regclass('public.product') IS NOT NULL").fetchone()[0]
+    if not has_product:
+        c.close()
+        pytest.skip("migrations not applied")
+    yield c
+    c.rollback()
+    c.close()
+
+
+def test_load_record_roundtrip(conn):
+    source_id = ensure_source(conn)
+    rec = transform(FIXTURE)
+    product_id = load_record(conn, rec, source_id, FIXTURE)
+
+    row = conn.execute(
+        "SELECT name, gtin, net_content_unit FROM product WHERE id = %s", (product_id,)
+    ).fetchone()
+    assert row[0] == "Nutella"
+    assert row[1] == "3017624010701"
+    assert row[2] == "g"
+
+    nutri = conn.execute(
+        "SELECT nutriments ->> 'energy_kcal' FROM food_detail WHERE product_id = %s",
+        (product_id,),
+    ).fetchone()
+    assert nutri[0] == "539.0"
+
+    prov = conn.execute(
+        "SELECT count(*) FROM product_source WHERE product_id = %s", (product_id,)
+    ).fetchone()
+    assert prov[0] >= 1
+
+    conn.rollback()  # keep the test DB clean