feat: 添加租后须知功能并优化发布默认设置

新增功能：
- 添加租后须知查看功能（PC端+移动端）
- 管理后台支持配置租后须知内容
- 默认提供完整的租后须知模板

功能实现：
- 后端：新增 PostRentalNotice API 接口和配置管理
- PC端：在用户下拉菜单添加租后须知入口，独立页面展示
- 移动端：在个人中心实名认证下方添加入口，弹窗展示
- 管理端：新增租后须知配置弹窗，支持编辑和恢复默认

优化改进：
- 修复发布页面默认选中"参考比例"而非"自定比例"
- 移除错误的迁移测试脚本（与 MySQL 8.0 不兼容）

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

frontend/src/features/auth/views/MobileProfileView.vue

@@ -6,6 +6,7 @@ import { showDialog, showToast } from "vant";
 import MobileBottomNav from "@/components/MobileBottomNav.vue";
 
 import { fetchWalletBalance, fetchWalletLedger, type WalletLedger } from "@/features/wallet/api/wallet";
+import { fetchPostRentalNotice, type PostRentalNotice } from "@/features/orders/api/orders";
 import { formatDateMinute } from "@/utils/time";
 import { uploadFile } from "@/shared/api/files";
 
@@ -60,6 +61,11 @@ const showLedgers = ref(false);
 const loadingLedgers = ref(false);
 const ledgers = ref<WalletLedger[]>([]);
 
+// 租后须知
+const showPostRentalNotice = ref(false);
+const loadingPostRentalNotice = ref(false);
+const postRentalNotice = ref<PostRentalNotice | null>(null);
+
 const settingsGroups = [
   {
     title: "账号与安全",
@@ -108,6 +114,20 @@ async function openLedgers() {
   }
 }
 
+async function openPostRentalNotice() {
+  showPostRentalNotice.value = true;
+  if (!postRentalNotice.value) {
+    loadingPostRentalNotice.value = true;
+    try {
+      postRentalNotice.value = await fetchPostRentalNotice();
+    } catch {
+      showToast({ message: "无法获取租后须知", icon: "cross" });
+    } finally {
+      loadingPostRentalNotice.value = false;
+    }
+  }
+}
+
 function handleWithdraw() {
   showDialog({
     title: "提现提示",
@@ -348,6 +368,7 @@ function resolveAvatarURL(url: string | undefined | null) {
               </span>
             </template>
           </van-cell>
+          <van-cell title="租后须知" icon="info-o" is-link @click="openPostRentalNotice" />
           <van-cell title="系统设置" icon="setting-o" is-link @click="showSettings = true" />
         </van-cell-group>
       </div>
@@ -382,6 +403,27 @@ function resolveAvatarURL(url: string | undefined | null) {
       </div>
     </van-popup>
 
+    <!-- 租后须知 Popup -->
+    <van-popup
+      v-model:show="showPostRentalNotice"
+      position="bottom"
+      round
+      class="notice-popup"
+      :style="{ height: '75%' }"
+    >
+      <header class="popup-header">
+        <h3>{{ postRentalNotice?.title || '租后须知' }}</h3>
+        <button class="popup-close" @click="showPostRentalNotice = false">✕</button>
+      </header>
+      <div class="popup-body">
+        <van-loading v-if="loadingPostRentalNotice" class="center-loading" vertical>加载中...</van-loading>
+        <div v-else-if="postRentalNotice" class="notice-content">
+          {{ postRentalNotice.content }}
+        </div>
+        <van-empty v-else description="暂无租后须知" />
+      </div>
+    </van-popup>
+
     <!-- 设置面板 - Popup -->
     <van-popup
       v-model:show="showSettings"
@@ -858,6 +900,26 @@ function resolveAvatarURL(url: string | undefined | null) {
   color: #ef4444;
 }
 
+/* 租后须知 Popup */
+.notice-popup {
+  display: flex;
+  flex-direction: column;
+}
+.notice-content {
+  padding: 16px 0;
+  color: #374151;
+  font-size: 14px;
+  line-height: 1.8;
+  white-space: pre-wrap;
+  word-wrap: break-word;
+}
+.center-loading {
+  display: flex;
+  align-items: center;
+  justify-content: center;
+  padding: 40px 0;
+}
+
 /* ========== 设置面板 ========== */
 .settings-panel {
   display: flex;