Add Celery as an executor and refactor threading logic

[torkashvand]

• Implement Celery for task execution
• Refactor code to improve thread handling and structure

[codecov]

Codecov Report

Attention: Patch coverage is 85.86957% with 13 lines in your changes missing coverage. Please review.

Project coverage is 86.98%. Comparing base (266deac) to head (3033fc5).

Files with missing lines	Patch %	Lines
lso/worker.py	64.28%	3 Missing and 2 partials ⚠️
lso/routes/playbook.py	85.00%	2 Missing and 1 partial ⚠️
lso/tasks.py	84.21%	2 Missing and 1 partial ⚠️
lso/playbook.py	89.47%	0 Missing and 2 partials ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main      #41      +/-   ##
==========================================
+ Coverage   85.71%   86.98%   +1.26%     
==========================================
  Files           7        9       +2     
  Lines         133      169      +36     
  Branches        6       12       +6     
==========================================
+ Hits          114      147      +33     
  Misses         15       15              
- Partials        4        7       +3     

☔ View full report in Codecov by Sentry.
📢 Have feedback on the report? Share it here.