feat(frontend): add React dashboard with TypeScript

Add modern React frontend to replace Streamlit dashboard:
- Vite build system with TypeScript
- Tailwind CSS for styling
- Component structure in src/
- Production Dockerfile with nginx
- Development server on port 5173

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

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

frontend/.gitignore

@@ -0,0 +1,22 @@
+# Dependencies
+node_modules/
+
+# Build output
+dist/
+
+# Local env files
+.env.local
+.env.*.local
+
+# Editor directories
+.vscode/
+.idea/
+
+# OS files
+.DS_Store
+Thumbs.db
+
+# Debug logs
+npm-debug.log*
+yarn-debug.log*
+yarn-error.log*