Build Wise Employee Portal UI

Add a comprehensive Employee Spending Portal page with a Wise-inspired layout: - Introduce EmployeeHeader and EmployeeHero components for navigation and messaging - Add budget overview, spending breakdown, and recent transactions sections - Create supporting components (SpendingBreakdown, RecentTransactions) to display department budgets, spend by category, and activity - Wire up placeholder EmployeePortal page to present a rich, empowering dashboard for employees to track department budgets and spending X-Lovable-Edit-ID: edt-a42a4638-a535-42eb-ab1e-c2bc32d0a2b6