Show LOC on concluded rankings

[msaroufim]

Summary

• Move LOC display to the main ranking rows for concluded competitions.
• Keep line_count on /api/leaderboard ranking rows instead of /api/codes/code drawer metadata.
• Remove the extra code-drawer LOC path and tests introduced in Show LOC for public solutions #248.
• Remove the old leaderboard 598 code-view block so concluded leaderboards are handled consistently.

Validation

• git diff --check
• .venv/bin/ruff check kernelboard/api/leaderboard.py kernelboard/api/submission.py tests/api/test_submission_api.py
• npm run lint
• npm run build

Notes

• Backend route pytest still requires Docker for the Postgres/Redis fixtures; Docker is not running in this local environment.