feat: Complete Material-UI migration for all pages

- Updated Dashboard page to use Material-UI components
- Updated SignupPage to use Material-UI with Google OAuth style
- Fixed Material-UI icon import issues (replaced Activity with Timeline)
- Updated CLAUDE.md to reflect UI framework migration from Lucide/Tailwind to Material-UI
- All pages now follow consistent Google OAuth design pattern

🤖 Generated with [Claude Code](https://claude.ai/code)

Co-Authored-By: Claude <noreply@anthropic.com>

CLAUDE.md

@@ -25,7 +25,10 @@
 
 ### 기술 스택
 - **API Gateway**: Apache APISIX 3.8.0
-- **Frontend**: React 18 + Vite + TypeScript + shadcn/ui + Tailwind CSS
+- **Frontend**: React 18 + Vite + TypeScript + Material-UI (MUI)
+  - 이전: Lucide React + Tailwind CSS
+  - 현재: Material-UI (@mui/material, @emotion/react, @emotion/styled, @mui/icons-material)
+  - 디자인: Google OAuth 스타일 UI/UX
 - **Backend**: Python 3.11 + FastAPI + Motor (MongoDB async)
 - **Database**: MongoDB 7.0
 - **Cache/Queue**: Redis 7