refactor: UI刷新とコード品質向上のためのリファクタリング ...

- lib.rs: ネスト解消、モジュール分割、パス解決とDB変換ロジックの共通化
- index.html: CSS, JSの外部ファイル化 (index.css, index.js)
- UI: タブ切り替え時のバグ修正、MCP設定表示の安定化
- README: システム概要と最新の更新内容を反映
- analyze_nesting.js & count_lines.js に基づく品質改善を確認済み

feat: add sidecar status indicator to UI

chore: release v0.1.1

chore: migrate to Tauri/Rust backend with SeaORM and add unit/integration tests ...

- Migrated Electron/Bun backend to Rust (Tauri v2).
- Integrated SeaORM with SQLite and sqlite-vec support.
- Implemented unit tests for LlamaClient and database initialization.
- Added integration tests for MCP handlers.
- Updated documentation (README.md, walkthrough, implementation plan).
- Improved dev environment with launch scripts and tasks.
- Followed user global rules for journaling and gitignore.