fix: 学生管理出生年月改为出生日期(YYYY-MM-DD)

1. 新增/编辑弹窗：日期选择器从月份改为日期
2. 列表页：出生日期列显示完整日期格式

frontend/ruoyi-ui/src/views/business/student/components/StudentDialog.vue

@@ -26,13 +26,13 @@
           <el-radio value="0">未知</el-radio>
         </el-radio-group>
       </el-form-item>
-      <el-form-item label="出生年月" prop="birthday">
+      <el-form-item label="出生日期" prop="birthday">
         <el-date-picker
           v-model="form.birthday"
-          type="month"
-          placeholder="请选择出生年月"
-          format="YYYY-MM"
-          value-format="YYYY-MM"
+          type="date"
+          placeholder="请选择出生日期"
+          format="YYYY-MM-DD"
+          value-format="YYYY-MM-DD"
           style="width: 100%"
         />
       </el-form-item>
@@ -161,7 +161,8 @@ const formatBirthday = (date) => {
   const d = new Date(date)
   const year = d.getFullYear()
   const month = String(d.getMonth() + 1).padStart(2, '0')
-  return `${year}-${month}`
+  const day = String(d.getDate()).padStart(2, '0')
+  return `${year}-${month}-${day}`
 }
 
 // 学校选择变化

frontend/ruoyi-ui/src/views/business/student/index.vue

@@ -65,7 +65,7 @@
                 {{ row.gender === '1' ? '男' : row.gender === '2' ? '女' : '未知' }}
               </template>
             </el-table-column>
-            <el-table-column prop="birthday" label="出生年月" width="100">
+            <el-table-column prop="birthday" label="出生日期" width="110">
               <template #default="{ row }">
                 {{ row.birthday ? formatDate(row.birthday) : '' }}
               </template>
@@ -244,7 +244,8 @@ const formatDate = (date) => {
   const d = new Date(date)
   const year = d.getFullYear()
   const month = String(d.getMonth() + 1).padStart(2, '0')
-  return `${year}-${month}`
+  const day = String(d.getDate()).padStart(2, '0')
+  return `${year}-${month}-${day}`
 }
 
 // 删除