feat: revamp homepage with chat simulation, comparison, use cases, FAQ (#13)

- Add typewriter chat simulation in hero (3 demo scenes, EN/ZH, auto-cycling)
- Hero: two-column layout on widescreen (left text + right chat), stacked on mobile
- Chat window with input bar, send button, online indicator, message bubbles
- Add comparison table: PicoClaw vs OpenClaw vs NanoBot with chart image
- Add 6 use case cards: code, content, data, assistant, research, API
- Add 6 FAQ items with collapsible panels
- Add demo section with 3 animated GIFs (code, memory, search)
- Add hardware compatibility banner with $9.9/$30/$50 product cards
- Move image assets to public/assets/ for better organization
- Add GitHub link to nav on changelog and download pages
- Replace all unicode escapes with direct Chinese text
- Responsive: 1024px breakpoint for column→stack transition

Co-authored-by: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

Author: imguoguo

public/assets/compare.jpg

@@ -19,6 +19,7 @@ const GITHUB_BASE = 'https://github.com/sipeed/picoclaw/releases/tag/';
       <a href="/download/" class="nav-link" data-i18n="nav-download">Download</a>
       <a href="/changelog/" class="nav-link active" data-i18n="nav-changelog">Changelog</a>
       <a href="https://docs.picoclaw.io" target="_blank" rel="noopener noreferrer" class="nav-link" data-i18n="nav-docs">Docs</a>
+      <a href="https://github.com/sipeed/picoclaw" target="_blank" rel="noopener noreferrer" class="nav-link">GitHub</a>
     </div>
     <div class="lang-toggle" id="lang-toggle">
       <button class="lang-btn active" data-lang="en">EN</button>

public/assets/hardware-banner.jpg

@@ -15,6 +15,7 @@ import Base from '../layouts/Base.astro';
       <a href="/download/" class="nav-link active" data-i18n="nav-download">Download</a>
       <a href="/changelog/" class="nav-link" data-i18n="nav-changelog">Changelog</a>
       <a href="https://docs.picoclaw.io" target="_blank" rel="noopener noreferrer" class="nav-link" data-i18n="nav-docs">Docs</a>
+      <a href="https://github.com/sipeed/picoclaw" target="_blank" rel="noopener noreferrer" class="nav-link">GitHub</a>
     </div>
     <div class="lang-toggle" id="lang-toggle">
       <button class="lang-btn" data-lang="en">EN</button>