Right sidebar property editor redesign

[zhenyu-cpu]

Question

How should the right sidebar property editor be redesigned to match the reference UI?

Context

The reference site shows an extensive right sidebar with:

• 纸张 (Paper) section: paper size selector (A3/A4/A5/B3/B4/B5/custom), width/height inputs, unit selector
• 打印设置 (Print Settings) section: number of copies, print method (canvas/pdf), scale options
• 页边距 (Margins) section: top/right/bottom/left margin inputs
• 页码 (Page Numbers) section: page number format and position
• 背景 (Background) section: background color/image
• 水印 (Watermark) section: watermark text, rotation, opacity
• 对齐 (Alignment) section: alignment tools
• Element-specific properties when an element is selected

Current state

The existing design page has a right sidebar with basic element properties (width, height, fontSize, etc.) but lacks the paper/print configuration sections.

Key decisions needed

1. Use Antdv Collapse/Accordion for sections or a scrollable form?
2. How to organize paper settings vs element-specific properties?
3. Should paper settings be global (apply to whole template) or per-page?
4. Property change debounce for canvas updates?

Depends on

Map issue #213