feat: add annotation types management system
- Created annotation_types table with name, display_name, color, category, icon
- Implemented CRUD API endpoints for annotation types management
- Built annotation types management UI page at /annotation-types
- Updated Toolbox component to dynamically load and display annotation types
- Updated CandleChart component to use dynamic annotation types for markers
- Added seed functionality for default types (break_up, break_down, line)
- Cleaned up duplicate migration files
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