7b3e94d6dc
- Add AgentSession database entity with SQLite persistence - Implement AgentSession CRUD operations in repository layer - Update executor to use hybrid cache + database approach - Add session restoration on startup (LoadActiveSessionsFromDB) - Link comments to agent sessions via agent_session_id - Fix SQLite NULL handling for nullable task fields - Add dev database setup with seed data (make dev, make dev-db-reset) - Update Makefile with dev targets for development mode This enables agent sessions to persist across backend restarts, solving the 'execution not found' error for resumed conversations.