fix: check celery worker's health

[SKairinos]

This change is 

[faucomte97]

Reviewed 4 of 4 files at r1, all commit messages.
Reviewable status: complete! all files reviewed, all discussions resolved (waiting on @SKairinos)

[codecov]

Codecov Report

Attention: Patch coverage is 21.12676% with 56 lines in your changes missing coverage. Please review.

Project coverage is 68.52%. Comparing base (837c9a1) to head (7e16906).
Report is 1 commits behind head on main.

Files with missing lines	Patch %	Lines
codeforlife/views/health_check.py	21.42%	55 Missing ⚠️
codeforlife/server.py	0.00%	1 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #163      +/-   ##
==========================================
- Coverage   69.52%   68.52%   -1.01%     
==========================================
  Files         124      124              
  Lines        2904     2967      +63     
==========================================
+ Hits         2019     2033      +14     
- Misses        885      934      +49     

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