refactor: 统一二级页面返回按钮样式

- 新增 page-back-btn 统一样式类，替换 dev-back-btn 和 console-back-btn
- 所有二级页面返回按钮移至页面左上角
- 表单页面补充底部取消按钮
- 新增 page-navigation spec 文档
- 补充工作台 mySkills 和 skillConfig 页面标题配置

src/styles/components/_index.scss

@@ -16,3 +16,13 @@
 @forward 'password-input';
 @forward 'search-bar';
 @forward 'stat-card';
+
+.page-back-btn {
+    display: inline-flex;
+    align-items: center;
+    gap: 6px;
+    cursor: pointer;
+    color: var(--color-primary);
+    font-weight: 600;
+    margin-bottom: 16px;
+}

src/styles/pages/_developer.scss

@@ -2,17 +2,6 @@
 
 @use '../tokens' as *;
 
-// 开发台返回按钮
-.dev-back-btn {
-    display: inline-flex;
-    align-items: center;
-    gap: 6px;
-    cursor: pointer;
-    color: var(--color-primary);
-    font-weight: 600;
-    margin-bottom: 16px;
-}
-
 // 开发台详情
 .dev-detail-header {
     display: flex;