- Add Budget Settings section to ConfigTab with token limit, usage threshold, budget period, and reset day inputs
- Add budget usage badge to DashboardTab showing token consumption and threshold warning
- Add budget API functions to api.ts (getBudgetSummary, updateBudgetConfig, deleteBudgetUsage)
- Add budget routes to routes.ts for GET/PATCH/DELETE agent budget endpoints
- Add CSS styles for budget progress bar, warning indicators, and section layout
- Add comprehensive tests for budget UI components and API routes