chore: 移除上传导图 + 优化复习引导提示

- 删除 ReviewMindMap 接口及 upload/get/upsert API
- 删除 ReviewDetail 上传 UI 和思维导图预览
- 回忆复习按钮移至内容元信息区
- 引导提示改为渐进式：折叠时引导展开，展开后引导点击节点
- 提示语用告知语气，无表情符号

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

src/components/ReviewRecall.vue

@@ -418,6 +418,11 @@ onMounted(() => {
       </div>
     </article>
 
+    <!-- 折叠时引导：告知用户展开标准导图 -->
+    <div v-if="!focusPath && !hasCompared && !standardExpanded" class="start-guide surface-card">
+      <p>展开下方「标准思维导图」后，可点击节点选择复习起点，然后在此凭记忆补全知识点。</p>
+    </div>
+
     <!-- 回忆输入：可编辑思维导图 -->
     <article class="surface-card recall-panel">
       <div class="panel-header">
@@ -509,8 +514,8 @@ onMounted(() => {
           <span>来源：{{ standard.generator }}</span>
           <span>参考：{{ standard.sourceReportCount }} 份报告 + {{ standard.sourceFragmentCount }} 份残片</span>
         </div>
-        <p v-if="!hasCompared && !focusPath" class="select-hint">
-          点击导图节点选择复习起点，选好后开始回忆填空
+        <p v-if="!focusPath && !hasCompared" class="select-hint">
+          点击导图节点即可选择复习起点，选好后凭记忆在上方补全知识点。
         </p>
         <MindMapViewer
           v-if="standardTree"
@@ -838,13 +843,27 @@ onMounted(() => {
   flex-shrink: 0;
 }
 
+.start-guide {
+  padding: 14px 22px;
+  background: linear-gradient(135deg, #fff8e1 0%, #fff3cd 100%);
+  border-left: 4px solid #ffc107;
+  border-radius: 8px;
+  font-size: 14px;
+  line-height: 1.6;
+  color: #856404;
+}
+
+.start-guide p {
+  margin: 0;
+}
+
 .select-hint {
   font-size: 13px;
-  color: #e6a23c;
+  color: #856404;
   margin: 0 0 8px;
   padding: 6px 12px;
   background: #fdf6ec;
   border-radius: 4px;
-  border-left: 3px solid #e6a23c;
+  border-left: 3px solid #ffc107;
 }
 </style>