Delete obsolete devlog entries related to JSON storage migration, deprecation, GitHub storage refactoring, and comprehensive field change tracking implementation. These changes include:

- Removed entry for migrating existing JSON devlog entries to PostgreSQL (ID: 287).
- Deleted entry for deprecating JSON storage and promoting PostgreSQL as the default (ID: 288).
- Removed entry for refactoring GitHub storage from primary storage to external integration (ID: 289).
- Deleted entry for implementing a comprehensive devlog field change tracking system (ID: 290).

Author: Marvin Zhang