feat(M1): 数据模型迁移 + GS1 GPC 食品分类 + 单位字典

- migrations/0001_init: 全部核心表(product/food_detail/product_msrp/product_source/brand/manufacturer/category/category_schema/unit/attribute_definition/product_image/merge_log) + 索引(gtin唯一/name trigram/JSONB GIN/category ltree/tsvector) + tsvector/updated_at 触发器
- 0002_seed_units: 单位字典(与 units.py 一致, 含中文别名) + 常用营养参数定义
- 0003_seed_categories: 食品品类骨架(GS1 GPC 映射 + 自建中文树, ltree) + 品类参数模板(营养基准 per_100g/ml)
- CI 增加 migrations job: 用 postgres service 跑 migrate up + down 验证可逆
- 本地实跑 up/down/re-up 全部通过

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

.github/workflows/ci.yml

@@ -43,3 +43,32 @@ jobs:
         run: ruff format --check .
       - name: Pytest
         run: pytest -q
+
+  migrations:
+    name: Migrations (postgres)
+    runs-on: ubuntu-latest
+    services:
+      postgres:
+        image: postgres:16-alpine
+        env:
+          POSTGRES_USER: opengoods
+          POSTGRES_PASSWORD: opengoods
+          POSTGRES_DB: opengoods
+        ports:
+          - "5432:5432"
+        options: >-
+          --health-cmd "pg_isready -U opengoods"
+          --health-interval 5s --health-timeout 5s --health-retries 10
+    env:
+      DBURL: postgres://opengoods:opengoods@localhost:5432/opengoods?sslmode=disable
+    steps:
+      - uses: actions/checkout@v4
+      - uses: actions/setup-go@v5
+        with:
+          go-version: "1.23"
+      - name: Install golang-migrate
+        run: go install -tags 'postgres' github.com/golang-migrate/migrate/v4/cmd/migrate@v4.18.1
+      - name: Migrate up
+        run: migrate -path migrations -database "$DBURL" up
+      - name: Migrate down (reversibility)
+        run: migrate -path migrations -database "$DBURL" down -all