feat(admin): authorize batch purchase starts

admin/internal/auth/session.go

@@ -62,6 +62,12 @@ func (manager *Manager) Ensure(writer http.ResponseWriter, request *http.Request
 	return current.csrfToken, false
 }
 
+// IsAuthenticated 只读检查当前请求是否持有有效管理会话；它不会像 Ensure 一样创建匿名会话。
+func (manager *Manager) IsAuthenticated(request *http.Request) bool {
+	_, current, found := manager.current(request)
+	return found && current.authenticated
+}
+
 // VerifyCSRF 只接受当前未过期会话中以恒定时间比较匹配的 token。
 func (manager *Manager) VerifyCSRF(request *http.Request, token string) (authenticated bool, ok bool) {
 	_, current, found := manager.current(request)

admin/internal/auth/session_test.go

@@ -37,6 +37,51 @@ func TestManagerRejectsTamperedAndExpiredCookies(t *testing.T) {
 	}
 }
 
+func TestIsAuthenticatedDoesNotCreateOrDependOnCSRFValidation(t *testing.T) {
+	manager := NewManager([]byte(strings.Repeat("s", 32)), false)
+	missingSession := httptest.NewRequest(http.MethodPost, "/tasks/start-purchases", nil)
+	if manager.IsAuthenticated(missingSession) {
+		t.Fatal("missing session was treated as authenticated")
+	}
+	if len(manager.sessions) != 0 {
+		t.Fatalf("read-only authentication check created %d sessions", len(manager.sessions))
+	}
+	anonymousRequest := httptest.NewRequest(http.MethodGet, "/login", nil)
+	anonymousResponse := httptest.NewRecorder()
+	manager.Ensure(anonymousResponse, anonymousRequest)
+	anonymousCookie := anonymousResponse.Result().Cookies()[0]
+	anonymousCheck := httptest.NewRequest(http.MethodPost, "/tasks/start-purchases", nil)
+	anonymousCheck.AddCookie(anonymousCookie)
+	if manager.IsAuthenticated(anonymousCheck) {
+		t.Fatal("anonymous CSRF session was treated as authenticated")
+	}
+
+	loginRequest := httptest.NewRequest(http.MethodPost, "/login", nil)
+	loginRequest.AddCookie(anonymousCookie)
+	authenticatedResponse := httptest.NewRecorder()
+	csrf := manager.RotateAuthenticated(authenticatedResponse, loginRequest)
+	authenticatedCookie := authenticatedResponse.Result().Cookies()[0]
+
+	authenticatedCheck := httptest.NewRequest(http.MethodPost, "/tasks/start-purchases", nil)
+	authenticatedCheck.AddCookie(authenticatedCookie)
+	if !manager.IsAuthenticated(authenticatedCheck) {
+		t.Fatal("valid authenticated session was not recognized")
+	}
+	if authenticated, csrfOK := manager.VerifyCSRF(authenticatedCheck, "wrong-token"); authenticated || csrfOK {
+		t.Fatalf("wrong token result = (%t, %t), want (false, false)", authenticated, csrfOK)
+	}
+
+	validRequest := httptest.NewRequest(http.MethodPost, "/tasks/start-purchases", nil)
+	validRequest.AddCookie(authenticatedCookie)
+	if authenticated, csrfOK := manager.VerifyCSRF(validRequest, csrf); !authenticated || !csrfOK {
+		t.Fatalf("valid token result = (%t, %t), want (true, true)", authenticated, csrfOK)
+	}
+
+	if authenticated, csrfOK := manager.VerifyCSRF(httptest.NewRequest(http.MethodPost, "/tasks/start-purchases", nil), csrf); authenticated || csrfOK {
+		t.Fatalf("missing session result = (%t, %t), want (false, false)", authenticated, csrfOK)
+	}
+}
+
 func flipCookieValue(t *testing.T, value string) string {
 	t.Helper()
 	if value == "" {