Fix/camera list resilient s3 image url

[fe51]

Fixes #553 "GET /cameras/ fails entirely when a single camera's S3 image is unavailable"

This PR introduces the following modifications

• Schema (CameraRead.last_image_url): updated field description to document that null is returned when the image is not yet uploaded or temporarily unavailable in S3
• GET /cameras/: added description on the route documenting the null fallback behavior for last_image_url
• GET /cameras/{camera_id}: same documentation addition as above
• fetch_cameras / get_camera: last_image_url resolution is now wrapped in a try/except — any HTTPException raised by the S3 presign call is caught and the field falls back to null instead of aborting the response

[codecov]

Codecov Report

❌ Patch coverage is 62.50000% with 6 lines in your changes missing coverage. Please review.
✅ Project coverage is 88.07%. Comparing base (1c546d5) to head (7b41f49).
⚠️ Report is 1 commits behind head on main.

Files with missing lines	Patch %	Lines
src/app/api/api_v1/endpoints/cameras.py	57.14%	6 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #554      +/-   ##
==========================================
- Coverage   88.16%   88.07%   -0.10%     
==========================================
  Files          51       51              
  Lines        2138     2147       +9     
==========================================
+ Hits         1885     1891       +6     
- Misses        253      256       +3     

Flag	Coverage Δ
backend	88.09% <62.50%> (-0.10%)	⬇️
client	87.80% <ø> (ø)

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[MateoLostanlen]

thanks for you fix @fe51

[fe51]

Last check :

• Launch services via pyro-envdev
• call camera endpoints successfully
• delete the last image on s3 of camera 1
• call endpoints again, no error, just, as expected, an empty path for last image url