feat(grade): 实现年级管理的新增与删除功能

- 后端新增AddGradeReqVO和DeleteGradeReqVO请求对象
- GradeController添加新增和删除年级两个接口
- GradeService及其实现类实现新增和删除年级逻辑
- MyBatis映射新增插入和删除SQL语句
- 前端API新增addGrade和deleteGrade方法
- class.vue新增年级列表操作列及相关事件处理
- 新增AddGradeDialog组件用于输入新增年级名称
- 增加页面新增按钮及弹窗显示控制
- 实现删除年级的API调用与界面删除操作反馈

enlish-vue/src/pages/class.vue

@@ -71,12 +71,21 @@
                             :current-row-key="selectedGradeId" @row-click="onGradeRowClick">
                             <el-table-column prop="id" label="ID" width="80" />
                             <el-table-column prop="title" label="年级名称" min-width="160" />
+                            <el-table-column label="操作" width="120" fixed="right">
+                                <template #default="{ row }">
+                                    <el-button type="danger" size="small" @click.stop="onDeleteGrade(row)">删除</el-button>
+                                </template>
+                            </el-table-column>
                         </el-table>
                         <div class="mt-4 flex justify-end">
                             <el-pagination background layout="prev, pager, next, sizes, total" :total="gradeTotalCount"
                                 :page-size="gradePageSize" :current-page="gradePageNo"
                                 @current-change="handleGradePageChange" @size-change="handleGradeSizeChange" />
                         </div>
+                        <div class="mt-3 flex justify-end">
+                            <el-button type="primary" @click="showAddGradeDialog = true">新增年级</el-button>
+                        </div>
+                        <AddGradeDialog v-model="showAddGradeDialog" @success="fetchGrades" />
                     </div>
 
                 </div>
@@ -90,9 +99,10 @@
 import Header from '@/layouts/components/Header.vue'
 import { ref, onMounted } from 'vue'
 import { getClassList } from '@/api/class'
-import { getGradeList } from '@/api/grade'
+import { getGradeList, deleteGrade } from '@/api/grade'
 import { getStudentList } from '@/api/student'
 import ExamGenerateDialog from '@/layouts/components/ExamGenerateDialog.vue'
+import AddGradeDialog from '@/layouts/components/AddGradeDialog.vue'
 
 const classes = ref([])
 const pageNo = ref(1)
@@ -111,6 +121,7 @@ const gradeLoading = ref(false)
 const gradeTableRef = ref(null)
 const selectedGradeId = ref(null)
 const selectedGradeTitle = ref('')
+const showAddGradeDialog = ref(false)
 
 const students = ref([])
 const studentPageNo = ref(1)
@@ -229,6 +240,21 @@ function resetStudentFilters() {
     fetchStudents()
 }
 
+async function onDeleteGrade(row) {
+    try {
+        await deleteGrade(row.id)
+        ElMessage.success('删除成功')
+        if (selectedGradeId.value === row.id) {
+            selectedGradeId.value = null
+            selectedGradeTitle.value = ''
+            gradeTableRef.value?.setCurrentRow()
+        }
+        await fetchGrades()
+    } catch (e) {
+        ElMessage.error('删除失败')
+    }
+}
+
 onMounted(() => {
     fetchClasses()
     fetchGrades()