feat(examples): comprehensive table-v2 demo page

Transform table-v2.vue into a detailed demo page demonstrating all
list-table-v2 features with 14 sections covering:

- Basic usage with pagination and events
- Styling (borders, alignment)
- Fixed columns (left/right)
- Data formatting (timestamp, filesize, dict)
- Custom cellRenderer with JSX
- Custom headerCellRenderer
- Dynamic height auto-probe
- Fixed height mode
- Column width distribution
- Height/maxHeight/headerHeight controls
- Slot-based custom cells
- i18n support
- Combined features stress test
- Renderer edge cases with pagination

Also fix .app-main overflow to enable page scrolling for demo.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

packages/manage/router/index.vue

@@ -199,7 +199,7 @@ body {
   min-height: 0 !important;
   display: flex !important;
   flex-direction: column !important;
-  overflow: hidden !important;
+  overflow-y: auto !important;
 }
 
 .el-header,