feat(apps): add T5 4.26" e-Paper clock example

[wzp100]

Add apps/tuya_t5_4.26inch_e-Paper-clock, a 4.26" e-Paper clock demo built on TuyaOpen.

• Include 4in26 e-Paper driver, GUI rendering, and font/image assets with default pin config
• Integrate Tuya IoT init and BLE/AP provisioning; button triggers netinfo clear and re-provisioning
• Sync time via Tuya cloud timestamp, with optional NTP fallback (EPD_CLOCK_ENABLE_NTP_FALLBACK)
• Handle DPs: time_mode (DPID 18, 12/24h) and night_mode (DPID 28) mapped to dark/light theme
• Persist settings in KV; add CLI helpers clock-reset / clock-wifi for debugging
• Refresh strategy: periodic full refresh to reduce ghosting; optional partial update path with alignment checks

Docs:

• Add README.md / README_CN.md covering wiring, build/flash/monitor, and config (src/tuya_config.h)
• Add app-level .gitignore for build outputs and local config

PR 描述/PR description

硬件型号：T5AI-Board 开发套件
主要功能：实现墨水屏时钟，以及手机app联动功能。
墨水屏型号：微雪4.26 英寸墨水屏
提供一个T5开发板墨水屏时钟的代码，可以实现手机配网，手机app控制墨水屏夜间模式以及显示进制功能。

代码质量/Code Quality:

在本次拉取请求中，我已考虑以下事项 As part of this pull request, I've considered the following:

• 确保代码注释和文档清晰，并使用英文注释以保证代码可读性。Ensure that the code comments and documentation are clear, and use English for comments to ensure code readability.
• 确保文件头遵循文件头格式。Ensure that the file header follows the File Header Format.
• 确保函数头遵循 Doxygen 格式。Ensure that function headers follow the Doxygen format as specified in Comments.
• 已查阅 编码风格指南，并核查代码风格合规性，包括缩进、空格、命名规范及其他风格要求。 Reviewed the Coding Style Guide and verified code style compliance, including indentation, spacing, naming conventions, and other style guidelines.
• 已使用代码格式化工具确保符合 TuyaOpen 编码规范。Have used the code-formatting source code formatting tool to ensure compliance with TuyaOpen coding standards.