feat: implement RAG dashboard with MUI and react-router

Add new RAG dashboard feature including:
- Main application layout with header and sidebar
- Multiple pages (Home, KnowledgeBase, PipelineConfig, Dashboard, MCP)
- Theme configuration and styling
- Routing setup with protected routes
- Login page and authentication flow
- Various UI components and mock data for dashboard views

src/components/Layout/Header.tsx

@@ -0,0 +1,73 @@
+import { Box, InputBase, styled } from '@mui/material';
+import SearchIcon from '@mui/icons-material/Search';
+import AccountCircleIcon from '@mui/icons-material/AccountCircle';
+
+const HeaderContainer = styled(Box)(({ theme }) => ({
+  display: 'flex',
+  alignItems: 'center',
+  padding: '0 20px',
+  height: '60px',
+  backgroundColor: '#FFFFFF',
+  color: '#333',
+  boxShadow: '0 1px 3px rgba(0,0,0,0.1)',
+  borderBottom: '1px solid #E5E5E5',
+}));
+
+const BrandTitle = styled(Box)(({ theme }) => ({
+  fontSize: '1.2rem',
+  fontWeight: 'bold',
+  color: '#333',
+}));
+
+const SearchBox = styled(Box)(({ theme }) => ({
+  display: 'flex',
+  alignItems: 'center',
+  backgroundColor: '#F8F9FA',
+  borderRadius: '6px',
+  padding: '6px 12px',
+  width: '320px',
+  border: '1px solid #E5E5E5',
+  marginLeft: 'auto',
+  marginRight: '20px',
+  '&:focus-within': {
+    borderColor: theme.palette.primary.main,
+    boxShadow: `0 0 0 2px rgba(226,0,116,0.1)`,
+  },
+  '& .MuiInputBase-input': {
+    border: 'none',
+    outline: 'none',
+    backgroundColor: 'transparent',
+    fontSize: '14px',
+    color: '#333',
+    '&::placeholder': {
+      color: '#999',
+    },
+  },
+}));
+
+const SearchInput = styled(InputBase)(({ theme }) => ({
+  marginLeft: '8px',
+  flex: 1,
+  fontSize: '0.875rem',
+}));
+
+const UserAvatar = styled(AccountCircleIcon)(({ theme }) => ({
+  color: '#666',
+  cursor: 'pointer',
+  fontSize: '2rem',
+}));
+
+const Header = () => {
+  return (
+    <HeaderContainer>
+      <BrandTitle>RAG Dashboard</BrandTitle>
+      <SearchBox>
+        <SearchIcon sx={{ color: '#999', fontSize: '1.2rem' }} />
+        <SearchInput placeholder="Search queries, KB names..." />
+      </SearchBox>
+      <UserAvatar titleAccess="User Profile" />
+    </HeaderContainer>
+  );
+};
+
+export default Header;