feat(pay): httpapi 加 CORS(web 跨域下单)+ 部署到 pangolin1 准备(#34/34A)

withCORS 中间件:仅白名单 origin(默认 pangolin.yanmeiai.com + pages.dev)返回 CORS 头、
OPTIONS 直接 204;New(svc, corsOrigins) + main 读 PAY_CORS_ORIGINS。为官网下单页跨域调 pay 铺路。

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

pay/cmd/paywatch/main.go

@@ -114,7 +114,7 @@ func main() {
 	defer stop()
 	go w.Loop(ctx, time.Duration(pollSec)*time.Second)
 
-	srv := &http.Server{Addr: addr, Handler: httpapi.New(svc), ReadHeaderTimeout: 10 * time.Second}
+	srv := &http.Server{Addr: addr, Handler: httpapi.New(svc, env("PAY_CORS_ORIGINS", "https://pangolin.yanmeiai.com,https://pangolin-site.pages.dev")), ReadHeaderTimeout: 10 * time.Second}
 	go func() {
 		log.Info("pangolin-pay listening", "addr", addr, "poll_seconds", pollSec)
 		if err := srv.ListenAndServe(); err != nil && err != http.ErrServerClosed {

pay/internal/httpapi/cors.go

@@ -0,0 +1,40 @@
+package httpapi
+
+import (
+	"net/http"
+	"strings"
+)
+
+// withCORS lets the browser storefront (pangolin website) call the order API
+// cross-origin. Auth is server-to-server / bearer-less here (no cookies), so
+// Allow-Credentials is not needed. Only whitelisted origins get CORS headers;
+// OPTIONS preflight is answered directly.
+func withCORS(next http.Handler, allowed map[string]bool) http.Handler {
+	return http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+		origin := r.Header.Get("Origin")
+		if origin != "" && allowed[origin] {
+			h := w.Header()
+			h.Set("Access-Control-Allow-Origin", origin)
+			h.Add("Vary", "Origin")
+			h.Set("Access-Control-Allow-Methods", "GET, POST, OPTIONS")
+			h.Set("Access-Control-Allow-Headers", "Content-Type")
+			h.Set("Access-Control-Max-Age", "600")
+		}
+		if r.Method == http.MethodOptions {
+			w.WriteHeader(http.StatusNoContent)
+			return
+		}
+		next.ServeHTTP(w, r)
+	})
+}
+
+// parseOrigins builds the allowed-origin set from a comma-separated list.
+func parseOrigins(csv string) map[string]bool {
+	m := map[string]bool{}
+	for _, o := range strings.Split(csv, ",") {
+		if o = strings.TrimSpace(o); o != "" {
+			m[o] = true
+		}
+	}
+	return m
+}

pay/internal/httpapi/handler.go

@@ -14,8 +14,9 @@ import (
 
 type Handler struct{ svc *pay.Service }
 
-// New wires the routes (Go 1.22 method+wildcard patterns).
+// New wires the routes (Go 1.22 method+wildcard patterns) and applies CORS for
-func New(svc *pay.Service) http.Handler {
+// the whitelisted browser origins (comma-separated; empty = no CORS headers).
+func New(svc *pay.Service, corsOrigins string) http.Handler {
 	h := &Handler{svc: svc}
 	mux := http.NewServeMux()
 	mux.HandleFunc("POST /order", h.createOrder)
@@ -24,7 +25,7 @@ func New(svc *pay.Service) http.Handler {
 		w.WriteHeader(http.StatusOK)
 		_, _ = w.Write([]byte("ok"))
 	})
-	return mux
+	return withCORS(mux, parseOrigins(corsOrigins))
 }
 
 type createReq struct {

pay/internal/httpapi/handler_test.go

@@ -16,7 +16,7 @@ const recvAddr = "TRecv00000000000000000000000000000A"
 func TestCreateGetAndConflict(t *testing.T) {
 	st, _ := store.Open(":memory:")
 	t.Cleanup(func() { _ = st.Close() })
-	srv := httptest.NewServer(New(pay.New(st, pay.Config{ReceiveAddress: recvAddr})))
+	srv := httptest.NewServer(New(pay.New(st, pay.Config{ReceiveAddress: recvAddr}), "https://pangolin.yanmeiai.com"))
 	t.Cleanup(srv.Close)
 
 	body, _ := json.Marshal(map[string]any{"user_ref": "u1", "sku": "pro-year", "amount": 5_000000})