fix(前端)：进度环方向 + 按钮颜色 + 删除确认 + 移除 console.log

- StartTask.vue：progress 计算改为 (total-current)/total*100，进度环从
  满到空递减（正确方向）
- ReviewDetail/ReviewRecall/MindMapViewer：type="primary" 全部改为
  type="success"，统一绿白主题
- Study.vue：删除任务增加 ElMessageBox.confirm 确认
- request.ts：移除全部 console.log

src/components/ReviewRecall.vue

@@ -328,7 +328,7 @@ onMounted(() => {
       <div class="panel-header">
         <h3>🧠 你的回忆</h3>
         <div class="panel-actions">
-          <el-button type="primary" :loading="comparing" @click="handleRecallCompare">
+          <el-button type="success" :loading="comparing" @click="handleRecallCompare">
             提交对比
           </el-button>
           <el-button v-if="hasCompared" @click="resetRecall">
@@ -389,7 +389,7 @@ onMounted(() => {
 
       <div v-if="!standard" class="empty-state">
         <el-empty description="暂无标准思维导图" :image-size="64">
-          <el-button type="primary" :loading="loading" @click="loadData">
+          <el-button type="success" :loading="loading" @click="loadData">
             生成
           </el-button>
         </el-empty>
@@ -400,7 +400,7 @@ onMounted(() => {
         <MindMapViewer ref="editViewer" :tree="standardTree" :editable="true" height="60vh" />
         <div class="edit-actions">
           <el-button @click="cancelStandardEdit">取消</el-button>
-          <el-button type="primary" :loading="savingStandard" @click="saveStandardEditFromViewer">
+          <el-button type="success" :loading="savingStandard" @click="saveStandardEditFromViewer">
             保存更新
           </el-button>
         </div>