fix(miners): normalize join conditions in getPullRequestsByRepo to LOWER() for case-insensitive repo matching

[Tet-9]

Summary

getPullRequestsByRepo in miners.service.ts joined the windows CTE on LOWER(p.repo_full_name) but then joined pr_review_summary and repos using exact-case p.repo_full_name. For any repo where rows in those tables were stored under a different casing variant than pull_requests.repo_full_name, both LEFT JOINs returned NULL — silently dropping review summary and repo metadata from scoring output for that miner.

Root Cause

-- Before (incorrect)
LEFT JOIN pr_review_summary rs ON rs.repo_full_name = p.repo_full_name
LEFT JOIN repos r ON r.repo_full_name = p.repo_full_name

-- After (correct)
LEFT JOIN pr_review_summary rs ON LOWER(rs.repo_full_name) = LOWER(p.repo_full_name)
LEFT JOIN repos r ON LOWER(r.repo_full_name) = LOWER(p.repo_full_name)

Changes

• packages/das/src/api/miners/miners.service.ts: normalized both LEFT JOIN conditions to use LOWER() on both sides, consistent with the windows CTE join.

Testing

Lint confirmed only pre-existing errors in cache.module.ts, unrelated to this change.

Fixes #152

[xiao-xiao-mao]

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