feat(M0): 工程地基 - Go API + Python 采集骨架 + CI + 数据契约

- api/: Go(chi) 只读 API 骨架, /healthz + 版本化路由(占位), Dockerfile, 单测
- ingestion/: Python 采集/ETL 包骨架, units 单位归一化(纯函数+测试), adapter 协议
- docker-compose.yml: postgres + redis + minio + api
- .github/workflows/ci.yml: Go build/vet/test + Python ruff/pytest
- docs/data-contract.md(两端共享契约) + docs/disclaimer.md(不提供购买声明)
- migrations/ 占位(M1 起填充)

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

ingestion/tests/test_units.py

@@ -0,0 +1,47 @@
+from decimal import Decimal
+
+import pytest
+
+from opengoods.units import (
+    UnitError,
+    canonical_unit_code,
+    kcal_to_kj,
+    kj_to_kcal,
+    normalize,
+)
+
+
+def test_normalize_mass_kg_to_g():
+    result = normalize("1.5", "kg")
+    assert result.dimension == "mass"
+    assert result.canonical_unit == "g"
+    assert result.canonical_value == Decimal("1500.0")
+
+
+def test_normalize_volume_litre_alias():
+    result = normalize(2, "升")
+    assert result.dimension == "volume"
+    assert result.canonical_value == Decimal("2000")
+    assert result.canonical_unit == "ml"
+
+
+def test_normalize_energy_kcal_to_kj():
+    result = normalize("539", "kcal")
+    assert result.dimension == "energy"
+    assert result.canonical_unit == "kJ"
+    assert result.canonical_value == Decimal("539") * Decimal("4.184")
+
+
+def test_canonical_unit_code_alias():
+    assert canonical_unit_code("公斤") == "kg"
+    assert canonical_unit_code(" G ") == "g"
+
+
+def test_unknown_unit_raises():
+    with pytest.raises(UnitError):
+        normalize(1, "parsec")
+
+
+def test_energy_roundtrip():
+    assert kcal_to_kj(1) == Decimal("4.184")
+    assert kj_to_kcal(Decimal("4.184")) == Decimal("1")