feat(ui): enhance frontend architecture and improve user experience

Refactor the frontend to use a more consistent design system and improve the overall user interface and experience.

- Implement a consistent use of `Card` components across various pages (Dashboard, Settings, Notes, etc.).
- Improve layout responsiveness and spacing in several modules.
- Enhance the Tasks page with drag-and-drop status updates and a Kanban-style view.
- Update the Calendar view with better color coding for task priorities and types.
- Refactor the Bookmarks page to use a grid layout with improved card previews.
- Update the Nginx configuration to handle SPA routing and health checks more effectively.
- Standardize import paths using `@/` aliases.
- Fix minor bugs in message sending and loading states.
- Update Docker configuration to build from source and use a specific backend port.

frontend/index.html

@@ -9,7 +9,6 @@
     <meta name="theme-color" content="#39b9ff" />
     <meta name="viewport" content="width=device-width, initial-scale=1.0" />
     <title>Trackeep - Your Self-Hosted Productivity & Knowledge Hub</title>
-    <link rel="stylesheet" crossorigin href="/assets/index-LnCEqXC_.css">
     <script>
       // Runtime environment variable injection
       window.ENV = {