fix: race condition caused duplicate course progress

[raizasafeel]

Summary

• Concurrent save_progress functions calls create duplicate LMS Course Progress rows for the same (member, lesson) before, now:
  • Added a before_insert that raises UniqueValidationError if row already exists
  • Wrapped the .save() calls in save_progress with try/except so duplicate inserts are silently ignored.
  • Added patch for cleaning up existing duplicates
  • Added a test for making sure duplicates are no longer created

[cypress]

lms    Run #3683

Run Properties:   Passed #3683  •  3a609a57e9 ℹ️: Merge 9081245dccb1c977e392dfda03e624c335681834 into 4860cf340b567bb1e1bf592ff795...

Project	lms
Branch Review	fix/course-progress
Run status	Passed #3683
Run duration	00m 45s
Commit	3a609a57e9 ℹ️: Merge 9081245dccb1c977e392dfda03e624c335681834 into 4860cf340b567bb1e1bf592ff795...
Committer	Raizaaa
View all properties for this run ↗︎

---

Test results
Failures	0
Flaky	1
Pending	0
Skipped	0
Passing	1
View all changes introduced in this branch ↗︎

[codecov-commenter]

Codecov Report

❌ Patch coverage is 65.21739% with 8 lines in your changes missing coverage. Please review.
✅ Project coverage is 47.84%. Comparing base (41fb007) to head (9081245).
⚠️ Report is 7 commits behind head on develop.

Files with missing lines	Patch %	Lines
lms/lms/doctype/course_lesson/course_lesson.py	0.00%	8 Missing ⚠️

Additional details and impacted files

@@             Coverage Diff             @@
##           develop    #2411      +/-   ##
===========================================
+ Coverage    47.74%   47.84%   +0.09%     
===========================================
  Files          150      150              
  Lines         6658     6680      +22     
===========================================
+ Hits          3179     3196      +17     
- Misses        3479     3484       +5     

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