docs: add board product images to bilingual README

[Y1hsiaochunnn]

Change / 变更

Add a compact visual board catalog to README.md and README_ZH.md. Each board has a 160-pixel-wide product thumbnail beside its model name, board definition, and official documentation links. The generated device/peripheral table is available in an expandable section below the catalog.

为中英文首页增加紧凑的图文板卡目录：每块板卡一行，左侧为统一宽度的产品缩略图，右侧为型号、板卡定义和官方文档入口。完整的设备与外设定义表保留在下方的可展开区域。

Images reuse the corresponding Waveshare product repositories through URLs pinned to their source commits. / 图片沿用对应微雪产品仓库的素材，并固定到来源提交。

Preview / 效果预览：English · 简体中文

Validation / 验证

• Bilingual Markdown audit: 0 errors and 0 warnings; documentation-only scope confirmed.
• Generated board table and documentation navigation checks passed.
• CI routing selects zero board builds for this documentation-only change.
• GitHub rendered preview: all four product images load successfully.

Hardware testing is not applicable to this README change. / 本次 README 变更不涉及实机测试。