refactor: enhance scheduler task detail page with improved UI and status handling
style: update scheduler overview page with new layout and styling for task statistics
feat: create placeholder portfolio and profile pages
chore: update SQLite database schema
- Introduced `scheduled_tasks` and `task_execution_logs` tables for managing scheduled tasks and their execution logs.
- Implemented CRUD operations for tasks in the scheduler service.
- Added API endpoints for task management including creation, retrieval, updating, deletion, and execution triggering.
- Implemented task execution logic for both function and HTTP tasks with retry and timeout handling.
- Added a task cleanup job to remove old execution logs.
- Introduced an executor pool to manage concurrent task executions.
- Registered a cleanup task for log management.
- Enhanced stats retrieval for total tasks, enabled tasks, and recent executions.
