[AAP-47039] Add dispatcherd worker health checks for project tasks

[hsong-rh]

https://issues.redhat.com/browse/AAP-47039

This PR includes:

• Add health check validation before project operations (create/sync/update)
• Return HTTP 503 when project workers are unavailable
• Add comprehensive error handling and test coverage

[codecov-commenter]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 91.17%. Comparing base (4888fdc) to head (16f4b87).

@@            Coverage Diff             @@
##             main    #1444      +/-   ##
==========================================
+ Coverage   91.14%   91.17%   +0.03%     
==========================================
  Files         234      234              
  Lines       10046    10070      +24     
==========================================
+ Hits         9156     9181      +25     
+ Misses        890      889       -1     

Flag	Coverage Δ
unit-int-tests-3.11	91.17% <100.00%> (+0.03%)	⬆️
unit-int-tests-3.12	91.17% <100.00%> (+0.03%)	⬆️

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Files with missing lines	Coverage Δ
src/aap_eda/api/exceptions.py	100.00% <100.00%> (ø)
src/aap_eda/api/views/project.py	100.00% <100.00%> (ø)
src/aap_eda/core/tasking/__init__.py	100.00% <100.00%> (+4.54%)	⬆️
src/aap_eda/tasks/orchestrator.py	73.43% <100.00%> (+0.27%)	⬆️
src/aap_eda/tasks/project.py	61.53% <100.00%> (+5.39%)	⬆️

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[sonarqubecloud]

Quality Gate passed

Issues
0 New issues
0 Accepted issues

Measures
0 Security Hotspots
100.0% Coverage on New Code
0.0% Duplication on New Code

See analysis details on SonarQube Cloud