fix(elm): Correctly append end-line partials in Elm processor

[sentry]

This PR addresses a TypeError: '<' not supported between instances of 'NoneType' and 'int' that occurred during the merging of coverage partials for Elm reports.

Root Cause:
The from_json function in apps/worker/services/report/languages/elm.py had a typo. For multi-line declarations, it incorrectly appended the end-of-span partial ([[None, ec, cov]]) to the start line (sl) instead of the end line (el). This led to two conflicting LineSession entries for the same line, one with [sc, None, cov] and another with [None, ec, cov]. When these were merged, the sorted(key=lambda p: p[0]) function attempted to compare None with an int, raising the TypeError in Python 3.

Changes Made:

1. Corrected partial append: Changed _file.append(sl, ...) to _file.append(el, ...) on line 46 in apps/worker/services/report/languages/elm.py. This ensures the end-of-span partial is correctly associated with its respective end line.
2. Optimized intermediate line handling: Adjusted the range for intermediate lines from range(sl, el) to range(sl + 1, el). This prevents redundant full-coverage appends to the start line, which is already handled by the initial append.

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Fixes WORKER-YTT

[codecov]

Codecov Report

❌ Patch coverage is 0% with 1 line in your changes missing coverage. Please review.
✅ Project coverage is 91.89%. Comparing base (7b60783) to head (c2aede3).
✅ All tests successful. No failed tests found.

Files with missing lines	Patch %	Lines
apps/worker/services/report/languages/elm.py	0.00%	1 Missing ⚠️

Additional details and impacted files

@@           Coverage Diff           @@
##             main    #1225   +/-   ##
=======================================
  Coverage   91.89%   91.89%           
=======================================
  Files        1325     1325           
  Lines       50862    50862           
  Branches     1626     1626           
=======================================
  Hits        46741    46741           
  Misses       3815     3815           
  Partials      306      306           

Flag	Coverage Δ
workerintegration	58.56% <0.00%> (ø)
workerunit	90.37% <0.00%> (ø)

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[codecov-notifications]

Codecov Report

❌ Patch coverage is 0% with 1 line in your changes missing coverage. Please review.
✅ All tests successful. No failed tests found.

Files with missing lines	Patch %	Lines
apps/worker/services/report/languages/elm.py	0.00%	1 Missing ⚠️

❌ Your patch check has failed because the patch coverage (0.00%) is below the target coverage (90.00%). You can increase the patch coverage or adjust the target coverage.

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