refactor(phone-image): CSS and HTML for thumbnail preview container

public/static/css/phone-image-templates.css

@@ -490,14 +490,45 @@
     opacity: 1;
 }
 
-/* --- 逐页对齐切换指示器 --- */
-.page-alignment-toggle {
+/* ============================================
+   Preview Thumbnails (缩略图容器)
+   ============================================ */
+.preview-thumbnails {
+    display: flex;
+    flex-direction: row;
+    align-items: flex-start;
+    gap: 20px;
+    height: 100%;
+    padding: 0 10px;
+}
+
+.preview-thumb-item {
+    position: relative;
+    flex-shrink: 0;
+    text-align: center;
+}
+
+.preview-thumb-item img {
+    display: block;
+    border: 1px solid #e0e0e0;
+    border-radius: 4px;
+    box-shadow: 0 2px 8px rgba(0,0,0,0.08);
+}
+
+.preview-thumb-page-num {
+    display: block;
+    text-align: center;
+    font-size: 12px;
+    color: #999;
+    margin-top: 6px;
+}
+
+.thumb-alignment-toggle {
     position: absolute;
     top: 8px;
     right: 8px;
     z-index: 10;
-    opacity: 0.5;
-    cursor: pointer;
+    opacity: 0;
     width: 24px;
     height: 24px;
     border-radius: 4px;
@@ -510,15 +541,46 @@
     user-select: none;
     border: none;
     padding: 0;
+    cursor: pointer;
+    transition: opacity 0.2s;
 }
 
-.page-alignment-toggle:hover {
+.preview-thumb-item:hover .thumb-alignment-toggle {
     opacity: 1;
+}
+
+.thumb-alignment-toggle:hover {
     background: rgba(0, 0, 0, 0.1);
 }
 
-.page-alignment-toggle.active-center {
+.thumb-alignment-toggle.active-center {
     opacity: 1;
     background: rgba(24, 144, 255, 0.15);
-    color: var(--pi-color-accent);
+    color: #1890ff;
+}
+
+/* ============================================
+   Content Flow Code Blocks (中间栏代码块样式)
+   仅用于编辑区中间栏, 不影响渲染页面
+   ============================================ */
+.content-flow pre {
+    background: #f5f5f5;
+    border: 1px solid #e0e0e0;
+    border-radius: 4px;
+    padding: 12px;
+    overflow-x: auto;
+    font-size: 13px;
+    line-height: 1.6;
+    margin: 10px 0;
+}
+
+.content-flow code {
+    font-family: 'Courier New', Consolas, monospace;
+    font-size: 13px;
+}
+
+.content-flow pre code {
+    background: none;
+    border: none;
+    padding: 0;
 }