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>

api/internal/handler/handler_test.go

@@ -0,0 +1,38 @@
+package handler
+
+import (
+	"encoding/json"
+	"net/http"
+	"net/http/httptest"
+	"testing"
+)
+
+func TestHealthz(t *testing.T) {
+	req := httptest.NewRequest(http.MethodGet, "/healthz", nil)
+	rec := httptest.NewRecorder()
+
+	Router().ServeHTTP(rec, req)
+
+	if rec.Code != http.StatusOK {
+		t.Fatalf("expected status %d, got %d", http.StatusOK, rec.Code)
+	}
+
+	var body map[string]string
+	if err := json.NewDecoder(rec.Body).Decode(&body); err != nil {
+		t.Fatalf("failed to decode body: %v", err)
+	}
+	if body["status"] != "ok" {
+		t.Fatalf("expected status ok, got %q", body["status"])
+	}
+}
+
+func TestProductEndpointNotImplemented(t *testing.T) {
+	req := httptest.NewRequest(http.MethodGet, "/api/"+APIVersion+"/products/barcode/3017624010701", nil)
+	rec := httptest.NewRecorder()
+
+	Router().ServeHTTP(rec, req)
+
+	if rec.Code != http.StatusNotImplemented {
+		t.Fatalf("expected status %d, got %d", http.StatusNotImplemented, rec.Code)
+	}
+}