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/pyproject.toml

@@ -5,6 +5,7 @@ description = "OpenGoods (天工·商品标签) ingestion & ETL: collect product
 requires-python = ">=3.11"
 dependencies = [
     "httpx>=0.27",
+    "psycopg[binary]>=3.2",
 ]
 
 [project.optional-dependencies]