feat: add mermaid diagram editor with rich visual tooling

[typelets]

Summary

Adds a Mermaid.js diagram editor as a first-class note type with interactive preview, zoom/pan controls, and export capabilities.

Features

Diagram Editor

• Monaco code editor with live Mermaid preview (25/75 default split)
• Auto-save (1.5s debounce), zoom (0.25x-3x), pan/drag navigation
• Theme-aware rendering + print optimization (forces light mode)
• Export: PNG (auto-crop), SVG, clipboard copy with visual confirmation
• 6 professional templates: flowchart, sequence, class, state, gantt, pie

UI Integration

• Create diagrams from notes panel (+ button → templates menu)
• Cyan Network icon indicator in note cards
• "Diagrams" filter option in filter dropdown
• Full CRUD support (star, hide, archive, delete, move to folder)

Mobile App Improvements

• Removed offline-first complexity (15+ files deleted)
• Simplified to API-driven architecture with smart caching
• Refactored screen structure for better maintainability

Backwards Compatibility

• Existing notes without type field work as regular notes
• Filter treats undefined type as non-diagram
• No breaking changes to API contracts

Bundle Impact

• DiagramEditor: ~50KB (lazy loaded)
• Mermaid: ~200KB (lazy loaded)
• Monaco: 3.6MB (already lazy loaded)

Testing

Manual testing completed:

• ✅ Diagram creation from templates
• ✅ Auto-save, export (PNG/SVG/clipboard)
• ✅ Zoom/pan, theme switching, print
• ✅ Filter functionality
• ✅ CRUD operations
• ✅ Mobile app navigation and caching

[github-actions]

🎉 This PR is included in version 1.33.0 🎉

The release is available on GitHub release

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