fix(core): Handle invalid Redis stream IDs in SSE endpoint

[sentry]

This PR addresses an issue where the /optimize/{job_id}/events SSE endpoint, when backed by Redis, would crash with a ResponseError: Invalid stream ID specified as stream command argument if the client provided a malformed Last-Event-ID header (e.g., 'invalid').

The root cause was that RedisJobStore.stream_events passed the client-controlled after_id (derived from Last-Event-ID) directly to Redis's xread command without validation. A truthy but malformed value would bypass the after_id or "0-0" fallback, leading to the Redis error.

The fix introduces a _normalize_stream_id helper function that validates the provided after_id. If after_id is None, empty, or does not conform to the expected Redis stream ID format (<ms>-<seq>), it now correctly defaults to "0-0". This ensures that streaming always starts from a valid point, preventing the ResponseError and mirroring the robust behavior already present in MemoryJobStore for invalid cursors.

Fixes NURSE-SCHEDULING-3D

[codecov]

Codecov Report

❌ Patch coverage is 76.92308% with 3 lines in your changes missing coverage. Please review.
✅ Project coverage is 92.62%. Comparing base (1c60cc8) to head (1ffb7ab).

Files with missing lines	Patch %	Lines
core/nurse_scheduling/server/stores/redis.py	76.92%	3 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##              dev      #54      +/-   ##
==========================================
- Coverage   92.65%   92.62%   -0.03%     
==========================================
  Files         100      100              
  Lines        8250     8262      +12     
  Branches      705      705              
==========================================
+ Hits         7644     7653       +9     
- Misses        460      463       +3     
  Partials      146      146              

Flag	Coverage Δ
core	94.11% <76.92%> (-0.04%)	⬇️
core-macos	94.13% <76.92%> (-0.04%)	⬇️
core-windows	94.11% <76.92%> (-0.04%)	⬇️
web-frontend	88.84% <ø> (ø)
web-frontend-macos	88.84% <ø> (ø)
web-frontend-windows	88.84% <ø> (ø)

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Files with missing lines	Coverage Δ
core/nurse_scheduling/server/stores/redis.py	96.56% <76.92%> (-0.61%)	⬇️

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