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.go

@@ -0,0 +1,68 @@
+// Package handler wires up the public, read-only OpenGoods HTTP API.
+//
+// The OpenGoods service is a public-good product information API: it only
+// collects and serves product facts. It exposes no purchase, checkout, or
+// commerce endpoints by design.
+package handler
+
+import (
+	"encoding/json"
+	"net/http"
+
+	"github.com/go-chi/chi/v5"
+	"github.com/go-chi/chi/v5/middleware"
+)
+
+// APIVersion is the current public API version prefix.
+const APIVersion = "v1"
+
+// Router builds the top-level HTTP handler with middleware and routes mounted.
+func Router() http.Handler {
+	r := chi.NewRouter()
+	r.Use(middleware.RequestID)
+	r.Use(middleware.RealIP)
+	r.Use(middleware.Recoverer)
+
+	r.Get("/healthz", Healthz)
+
+	r.Route("/api/"+APIVersion, func(r chi.Router) {
+		r.Route("/products", func(r chi.Router) {
+			r.Get("/barcode/{gtin}", notImplemented)
+			r.Get("/search", notImplemented)
+			r.Get("/{id}", notImplemented)
+			r.Get("/{id}/nutriments", notImplemented)
+			r.Get("/{id}/msrp", notImplemented)
+		})
+		r.Get("/brands", notImplemented)
+		r.Get("/categories", notImplemented)
+		r.Get("/sources/{id}", notImplemented)
+	})
+
+	return r
+}
+
+// Healthz reports liveness of the service.
+func Healthz(w http.ResponseWriter, r *http.Request) {
+	writeJSON(w, http.StatusOK, map[string]string{"status": "ok"})
+}
+
+// notImplemented is a placeholder for endpoints scoped to later milestones.
+func notImplemented(w http.ResponseWriter, r *http.Request) {
+	writeError(w, r, http.StatusNotImplemented, "not_implemented", "endpoint not implemented yet")
+}
+
+func writeJSON(w http.ResponseWriter, status int, body any) {
+	w.Header().Set("Content-Type", "application/json; charset=utf-8")
+	w.WriteHeader(status)
+	_ = json.NewEncoder(w).Encode(body)
+}
+
+func writeError(w http.ResponseWriter, r *http.Request, status int, code, message string) {
+	writeJSON(w, status, map[string]any{
+		"error": map[string]string{
+			"code":       code,
+			"message":    message,
+			"request_id": middleware.GetReqID(r.Context()),
+		},
+	})
+}