MDViewer mdviewer-v2.3.0

[mdviewer] Search and external reload prompts

## Summary
- Add sidebar markdown filename search with optional regex filtering
- Add per-tab viewer text find with highlighting, markdown-source counts, and case option
- Detect external file changes and prompt active tabs to reload latest content
- Bump MDViewer to v2.3.0

## Verification
- node --check 99.utils/00.MDViewer/src/app.js
- node --check 99.utils/00.MDViewer/src/tabs.js
- cargo check
- git diff --check
- npm run tauri -- build