fix: 创建有声书页底部操作栏上移，避免被底部 tab 栏遮挡

.bottom-bar 原 bottom:0 与 CustomTabBar(110rpx) 重叠，按钮只露一半。
改为 bottom:110rpx 置于 tab 栏之上，main-content padding-bottom 同步加大。

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

my-uniapp-vue3/src/pages/book-generator/create.vue

@@ -869,7 +869,7 @@ onLoad(async (query: any) => {
 
 .main-content {
   padding-top: calc(88rpx + 12rpx + env(safe-area-inset-top));
-  padding-bottom: 200rpx;
+  padding-bottom: 320rpx;
 }
 
 /* ========== 卡片 ========== */
@@ -1112,7 +1112,7 @@ onLoad(async (query: any) => {
 
 /* ========== 底部操作区 ========== */
 .bottom-bar {
-  position: fixed; bottom: 0; left: 0; right: 0;
+  position: fixed; bottom: 110rpx; left: 0; right: 0;
   padding: 20rpx 32rpx calc(20rpx + env(safe-area-inset-bottom));
   background: rgba(255,255,255,0.92);
   backdrop-filter: blur(20px);