fix: sse error handling

[sebastiendan]

Description

This PR fixes SSE error handling by verifying that the error is an application one in the first place. Additionally, the details of the error are now displayed on the Frontend (instead of only being sent to Tempo).

PR Checklist:

• I have performed a self-review of my code
• I have commented my code, particularly in hard-to-understand areas
• I have made corresponding changes to the documentation
• I have added or updated tests that comprehensively prove my change is effective or that my feature works

[codecov]

Codecov Report

Attention: 31 lines in your changes are missing coverage. Please review.

Comparison is base (19286dd) 85.77% compared to head (0f7db7d) 85.72%.

Files	Patch %	Lines
packages/frontend/src/hooks/useExecutorService.ts	29.54%	31 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main      #47      +/-   ##
==========================================
- Coverage   85.77%   85.72%   -0.06%     
==========================================
  Files          27       27              
  Lines        1378     1380       +2     
  Branches      127      127              
==========================================
+ Hits         1182     1183       +1     
- Misses        196      197       +1     

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