refactor(projects): assign + assign-batch 合并为单路由, 子页面 v-if 区分

- router 删 /assign-batch 路由, 仅保留 /assign (单条/批量都走)
- Projects.vue openAssign() 2 个 push 路径统一为 /manager/projects/assign
- 子页面面包屑加 v-if 批量模式 tag (橙色 badge 标识)
- 单/批模式区分完全靠 query.projectId vs query.projectIds + 子页面内 v-if/v-else 区块 (info-bar / 实时校验栏)

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

ry-vue3/src/router/index.js

@@ -62,7 +62,6 @@ const routes = [
       { path: 'projects/edit/:projectId', name: 'manager-projects-edit', component: () => import('@/views/manager/ProjectsNew.vue'), meta: { title: '编辑项目' } },
       { path: 'projects/detail/:projectId', name: 'manager-projects-detail', component: () => import('@/views/manager/ManagerProjectDetail.vue'), meta: { title: '项目详情' } },
       { path: 'projects/assign', name: 'manager-projects-assign', component: () => import('@/views/manager/ManagerProjectsAssign.vue'), meta: { title: '项目分配' } },
-      { path: 'projects/assign-batch', name: 'manager-projects-assign-batch', component: () => import('@/views/manager/ManagerProjectsAssign.vue'), meta: { title: '批量项目分配' } },
       { path: 'meetings', name: 'manager-meetings', component: () => import('@/views/manager/Meetings.vue'), meta: { title: '会议管理' } },
       { path: 'meetings/new', name: 'manager-meetings-new', component: () => import('@/views/manager/MeetingNew.vue'), meta: { title: '新建会议' } },
       { path: 'experts', name: 'manager-experts', component: () => import('@/views/expert/Experts.vue'), meta: { title: '专家审核' } },