Feat/mermaid copy button

[JWhiteCat]

Summary

Adds a copy button to Mermaid diagrams for easy source code copying on both Web and Mobile platforms.

Changes

• ✅ Copy button - Hover to show on Web, always visible on Mobile
• ✅ Clipboard integration - Copies raw Mermaid source code
• ✅ User feedback - Success/error modal alerts
• ✅ 10 languages - Full i18n support

Implementation

Key additions:

• copyMermaidSource() - Async clipboard copy handler
• renderCopyButton(visible) - Reusable button component
• Platform-specific visibility control (hover vs. always-on)

Files changed: 11 files (+72, -2)

• MermaidRenderer.tsx - Core functionality
• Translation files (ca, en, es, it, ja, pl, pt, ru, zh-Hans, zh-Hant)

Testing

Tested:

• ✅ Web (localhost:8081) - Hover, copy, paste
• ✅ Translations defined for all languages
• ⏳ Mobile - Pending device access

Test with:

```mermaid
graph TD;
    A[Start] --> B[End];
```

Design Decisions

1. Follows existing code block copy button pattern
2. DRY principle - Single reusable function
3. Mobile-friendly - No hidden hover states
4. Performance - Uses React.useCallback

---

Generated with Claude Code via Happy