Add active boolean field to Pose model

[MateoLostanlen]

Poses represent camera orientations that can change over time. Previously, all poses (including outdated ones)
were returned when fetching cameras, which cluttered the frontend with stale data. We still need to keep old
poses in the database for historical consistency (linked detections, sequences, etc.), so rather than deleting
them, we introduce an active boolean flag to soft-filter them.

• Add active boolean field to the Pose model (defaults to True)
• Camera endpoints (GET /cameras/{id} and GET /cameras/) now only return active poses
• Alembic migration sets server_default=true so all existing poses remain active
• Python client updated to support active in create_pose and update_pose

[codecov]

Codecov Report

❌ Patch coverage is 85.71429% with 2 lines in your changes missing coverage. Please review.
✅ Project coverage is 88.20%. Comparing base (b71cc17) to head (0e7fd36).

Files with missing lines	Patch %	Lines
client/pyroclient/client.py	85.71%	1 Missing ⚠️
src/app/api/api_v1/endpoints/detections.py	50.00%	1 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #564      +/-   ##
==========================================
+ Coverage   88.07%   88.20%   +0.13%     
==========================================
  Files          51       51              
  Lines        2147     2154       +7     
==========================================
+ Hits         1891     1900       +9     
+ Misses        256      254       -2     

Flag	Coverage Δ
backend	88.07% <85.71%> (-0.02%)	⬇️
client	90.40% <85.71%> (+2.59%)	⬆️

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