feat(frontend): Element Plus 改按需引入，首屏 425.1->158.8KB（R36）

- vite.config.js: 新增 unplugin-vue-components + ElementPlusResolver；
  optimizeDeps.include 动态生成 118 项无扩展名 specifier（glob/.mjs 皆静默失效）
- main.js: 删 app.use(ElementPlus) 与全量 CSS；改 provideGlobalConfig(locale, app, true)；
  显式引入 4 个函数式组件样式（message/message-box/notification/loading）
- views/Upload.vue: 3 处 h(resolveComponent('el-xxx')) 改显式组件引用；清 2 处死导入
- devDep: unplugin-vue-components@^32.1.0
- .gitignore: 忽略 vite.config.js.timestamp-*.mjs

验证：dist 渲染 9/9 · dist 登录后 9/9 · dev 通道致命错误 0/告警 0
瘦身：首屏 425.1->158.8KB(-62.6%)；主包 JS 1112.9->281.09KB

src/views/Upload.vue

@@ -136,7 +136,7 @@
  *   6. 上传历史列表
  *   7. 教师组双上传区（教学方案 + 说课PPT）
  */
-import { ref, computed, onMounted, onUnmounted, h, resolveComponent } from 'vue'
+import { ref, computed, onMounted, onUnmounted, h } from 'vue'
 import { ElMessage, ElMessageBox, ElUpload, ElProgress, ElButton, ElTag, ElIcon } from 'element-plus'
 import { ArrowLeft, HomeFilled, Clock, UploadFilled, Delete } from '@element-plus/icons-vue'
 import { useAuthStore } from '@/stores/auth'
@@ -305,7 +305,7 @@ onUnmounted(() => {
  * file-upload-area 是一个内联组件
  * 为了保持 Vue SFC 的简洁性，我们用 defineComponent
  */
-import { defineComponent, ref, reactive, h, resolveComponent, computed } from 'vue'
+import { defineComponent, ref, reactive, h, computed } from 'vue'
 import { ElMessage, ElUpload, ElProgress, ElButton, ElTag, ElIcon } from 'element-plus'
 import { UploadFilled, Delete } from '@element-plus/icons-vue'
 import * as uploadApi from '@/api/upload'
@@ -455,7 +455,7 @@ const FileUploadArea = defineComponent({
                 e.currentTarget.previousElementSibling?.click()
               },
             }, [
-              h(resolveComponent('el-icon'), { size: 48 }, () => h(UploadFilled)),
+              h(ElIcon, { size: 48 }, () => h(UploadFilled)),
               h('div', { class: 'drag-text' }, '拖拽文件到此处或 '),
               h('em', null, '点击上传'),
               h('div', { class: 'drag-hint' },
@@ -488,7 +488,7 @@ const FileUploadArea = defineComponent({
 
         // 上传进度
         uploading.value ? h('div', { class: 'upload-progress' }, [
-          h(resolveComponent('el-progress'), {
+          h(ElProgress, {
             percentage: uploadPercent.value,
             status: uploadPercent.value >= 100 ? 'success' : undefined,
           }),
@@ -496,7 +496,7 @@ const FileUploadArea = defineComponent({
 
         // 已上传文件信息
         uploadedInfo.value ? h('div', { class: 'uploaded-card' }, [
-          h(resolveComponent('el-tag'), { type: 'success', size: 'small' }, () => '上传成功'),
+          h(ElTag, { type: 'success', size: 'small' }, () => '上传成功'),
           h('div', { class: 'uploaded-name' }, uploadedInfo.value.fileName),
           h('div', { class: 'uploaded-meta' }, [
             h('span', null, formatFileSize(uploadedInfo.value.fileSize)),