feat: 购买下单透传终端类型，手机端收银台拉起支付宝 App（契约 v1.1.0）

根因：pay 判手机/PC 用下单请求 UA，而下单由 jiu 后端 Go client 发出，
恒被判 PC 扫码页——手机用户拿不到 wap 拉起页。

- backend：/license/purchase 请求体加可选 client_type（oneof=pc mobile），
  缺省按本请求 UA 兜底（官网浏览器购买自动受益）；CreatePurchase 透传给 pay；
  单测断言透传 + 既有用例补参
- client：createPurchase 支持 clientType；PurchaseCard 按平台声明
  （iOS/Android=mobile，桌面=pc，Web 不传走 UA），kIsWeb 先于 dart:io；
  launchUrl 外部浏览器不变，wap 收银台自动拉起支付宝
- 配套：pay-contract v1.1.0（744725b）+ pay 侧 resolveIsMobile（dbdadd1）已各自提交

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01JJ1g8XV1YhhmHRzhwWEW7o

backend/internal/service/pay.go

@@ -90,7 +90,10 @@ type PurchaseResult struct {
 }
 
 // CreatePurchase 建购买记录并调 pay 下单，返回收银台跳转 URL。
-func (s *PayService) CreatePurchase(shopID, userID uint64, bizCode string) (*PurchaseResult, error) {
+// clientType（契约 v1.1.0，"pc"/"mobile"/""）：显式端型透传给 pay 决定收银台形态
+// （mobile=手机网站支付拉起支付宝 App / pc=电脑扫码页）；服务端间调用下单请求 UA
+// 是本后端的，不传则 pay 会按 Go client UA 误判为 PC。
+func (s *PayService) CreatePurchase(shopID, userID uint64, bizCode, clientType string) (*PurchaseResult, error) {
 	if !s.Configured() {
 		return nil, ErrPayNotConfigured
 	}
@@ -117,12 +120,16 @@ func (s *PayService) CreatePurchase(shopID, userID uint64, bizCode string) (*Pur
 		return nil, err
 	}
 
-	reqBody, _ := json.Marshal(map[string]any{
+	payload := map[string]any{
 		"product_id": productID,
 		"biz_system": "jiu",
 		"biz_ref":    strconv.FormatUint(p.ID, 10),
 		"return_url": s.retURL,
-	})
+	}
+	if clientType != "" {
+		payload["client_type"] = clientType
+	}
+	reqBody, _ := json.Marshal(payload)
 	respBody, err := s.signedPost("/api/v1/orders", reqBody)
 	if err != nil {
 		return nil, fmt.Errorf("pay 下单失败: %w", err)

backend/internal/service/pay_test.go

@@ -234,7 +234,7 @@ func TestCreatePurchase_HappyPath(t *testing.T) {
 	mux.HandleFunc("GET /api/v1/products", func(w http.ResponseWriter, r *http.Request) {
 		fmt.Fprint(w, `{"data":[{"id":3,"biz_code":"annual_standard"},{"id":4,"biz_code":"monthly_pro"}]}`)
 	})
-	var gotBizRef string
+	var gotBizRef, gotClientType string
 	mux.HandleFunc("POST /api/v1/orders", func(w http.ResponseWriter, r *http.Request) {
 		body := make([]byte, r.ContentLength)
 		_, _ = r.Body.Read(body)
@@ -246,13 +246,14 @@ func TestCreatePurchase_HappyPath(t *testing.T) {
 		var req map[string]any
 		_ = json.Unmarshal(body, &req)
 		gotBizRef, _ = req["biz_ref"].(string)
+		gotClientType, _ = req["client_type"].(string)
 		fmt.Fprint(w, `{"data":{"pay_url":"https://openapi.alipay.com/gateway","out_trade_no":"yanmei-new-1","amount":"2999.00","subject":"年付标准"}}`)
 	})
 	payServer := httptest.NewServer(mux)
 	defer payServer.Close()
 
 	svc := newTestPaySvc(db, payServer.URL)
-	res, err := svc.CreatePurchase(shop.ID, 1, "annual_standard")
+	res, err := svc.CreatePurchase(shop.ID, 1, "annual_standard", "mobile")
 	require.NoError(t, err)
 	assert.Equal(t, "https://openapi.alipay.com/gateway", res.PayURL)
 	assert.Equal(t, "yanmei-new-1", res.OutTradeNo)
@@ -262,16 +263,17 @@ func TestCreatePurchase_HappyPath(t *testing.T) {
 	assert.Equal(t, "pending", p.Status)
 	assert.Equal(t, "2999.00", p.Amount)
 	assert.Equal(t, strconv.FormatUint(p.ID, 10), gotBizRef, "biz_ref 应为购买记录 id")
+	assert.Equal(t, "mobile", gotClientType, "client_type 应透传给 pay（契约 v1.1.0）")
 }
 
 func TestCreatePurchase_UnknownPlanAndUnconfigured(t *testing.T) {
 	db := testutil.SetupTestDB()
 	svc := newTestPaySvc(db, "http://pay.invalid")
-	_, err := svc.CreatePurchase(1, 1, "no_such_plan")
+	_, err := svc.CreatePurchase(1, 1, "no_such_plan", "pc")
 	assert.ErrorIs(t, err, ErrUnknownPlan)
 
 	unconfigured := NewPayService(db, "http://pay.invalid", "", "")
-	_, err = unconfigured.CreatePurchase(1, 1, "annual_standard")
+	_, err = unconfigured.CreatePurchase(1, 1, "annual_standard", "pc")
 	assert.ErrorIs(t, err, ErrPayNotConfigured)
 }
 
@@ -287,7 +289,7 @@ func TestCreatePurchase_PromoOncePerShop(t *testing.T) {
 	used, err := svc.PromoUsed(shop.ID)
 	require.NoError(t, err)
 	assert.False(t, used)
-	_, err = svc.CreatePurchase(shop.ID, 1, PromoBizCode)
+	_, err = svc.CreatePurchase(shop.ID, 1, PromoBizCode, "pc")
 	assert.NotErrorIs(t, err, ErrPromoUsed)
 
 	// pending 单不算已享用（可能弃单），仍可重新下单
@@ -302,7 +304,7 @@ func TestCreatePurchase_PromoOncePerShop(t *testing.T) {
 	used, err = svc.PromoUsed(shop.ID)
 	require.NoError(t, err)
 	assert.True(t, used)
-	_, err = svc.CreatePurchase(shop.ID, 1, PromoBizCode)
+	_, err = svc.CreatePurchase(shop.ID, 1, PromoBizCode, "pc")
 	assert.ErrorIs(t, err, ErrPromoUsed)
 
 	// 多租户隔离：别家买过不影响本店