feat(ui): rebuild homepage with new sections and i18n

This commit introduces a complete overhaul of the homepage, rebuilding it from the ground up with Nuxt UI and full
internationalization support. The new design better showcases the studio's capabilities and projects.

- Re-architected the index page with multiple new sections: Capabilities, Featured Projects, Tech Stack, and Why Choose Us.
- Implemented full i18n for English (en-US) and Chinese (zh-CN) across all new content.
- Centralized the page structure into a `default.vue` layout with a global header (including color mode and locale selectors) and
footer.
- Replaced placeholder logos with a dynamic `UMarquee` of technology icons using Iconify.

docs/design-doc-v1.md

@@ -120,13 +120,3 @@
 * 集成 **多语言支持（i18n）**，面向海外客户。
 * 游戏项目可接入 **WebGL / Godot Web Export**，直接可试玩。
 * 将案例模块化为 JSON / Markdown 文件，可持续维护。
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----
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-要不我直接帮你整理成一个完整的：
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-> 🧾《工作室网站重构计划书（v1）》——包括结构图、推荐技术栈、视觉方向与页面草稿说明。
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-格式我可以生成成 Word / PDF，你可以直接交给团队或自己用来开发。
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-是否要我现在帮你生成？（如果要，请告诉我希望输出哪种格式：**Word** 还是 **PDF**）