Removes the deprecated file-based task storage system as it has been 
replaced by the v2 Supabase-based system. This includes:
- Legacy in-memory task storage
- File persistence to tasks_backup.json  
- Deprecated run_ai_code_task() function
- Legacy Docker container execution code

Co-authored-by: Elwynn Chen <ObservedObserver@users.noreply.github.com>

Removes commented imports and function references to the deleted 
code_task_v1 module:
- Removed commented import of run_ai_code_task and _run_ai_code_task_internal
- Removed commented legacy function calls in sequential processor
- Simplified conditional logic to only handle v2 tasks

Co-authored-by: Elwynn Chen <ObservedObserver@users.noreply.github.com>