Backend: wrap SUM() queries with COALESCE in handle_time_series,
handle_clients_usage, and handle_detailed_usage to prevent NULL-induced
panics when no data exists for a time window.
Frontend: add showEmptyChart() empty-state messages and error feedback
across overview, analytics, costs, and clients pages. Rewrite analytics
loadCharts() to use Promise.allSettled() so each chart renders
independently on partial API failures.
- Added global loading spinner and page transitions.
- Improved sidebar with tooltips and persistent collapsed state.
- Fixed chart memory leaks by properly destroying instances on page change.
- Unified WebSocket event handling and status indicators.
- Refined stat cards, tables, and modal interactions.
- Added real backend integration for logout and session management.
- Switched from mock data to real backend APIs.
- Implemented unified ApiClient for consistent frontend data fetching.
- Refactored dashboard structure and styles for a modern SaaS aesthetic.
- Fixed Axum 0.8+ routing and parameter syntax issues.
- Implemented real client creation/deletion and provider health monitoring.
- Synchronized WebSocket event structures between backend and frontend.
