支持项目编码访问单项目公示屏

需求：无需查询公示 Token，直接通过项目编码打开单项目公示页。

实现：规范化项目编码并按 code 查询，同时保留既有 Token 哈希查询；补充前后端及集成回归测试。

server/internal/httpapi/rollover_integration_test.go

@@ -158,6 +158,22 @@ func TestCurrentDayViewsIgnoreYesterdayRunningSessionPostgresIntegration(t *test
 		}
 	})
 
+	t.Run("display by project code", func(t *testing.T) {
+		recorder := httptest.NewRecorder()
+		request := httptest.NewRequest(http.MethodGet, "/api/display/"+strings.ToLower(project.Code)+"/snapshot", nil)
+		server.Handler().ServeHTTP(recorder, request)
+		if recorder.Code != http.StatusOK {
+			t.Fatalf("status = %d, body = %s", recorder.Code, recorder.Body.String())
+		}
+		var response displaySnapshotDTO
+		if err := json.Unmarshal(recorder.Body.Bytes(), &response); err != nil {
+			t.Fatal(err)
+		}
+		if response.Project.ID != project.ID {
+			t.Fatalf("project = %q, want %q", response.Project.ID, project.ID)
+		}
+	})
+
 	t.Run("admin project", func(t *testing.T) {
 		projection, _, _, _, _, err := server.adminProjectProjection(context.Background(), project)
 		if err != nil {