fix(installation): case-insensitive repo removal and normalize PK

[Yurii214]

Fixes #120

Summary

• Add shared normalizeRepoFullName() / validateRepoFullName() utility
• Webhook installation_repositories.added stores lowercase canonical PK
• Webhook installation_repositories.removed clears rows case-insensitively
• Admin register/backfill paths normalize via shared validator
• Log a warning when removal updates zero rows (previously silent no-op)

Why

GitHub repo identity is case-insensitive, but PostgreSQL PK lookups are not.
Admin registration could create owner/repo while webhooks stored Owner/Repo,
so uninstall events returned HTTP 202 while leaving registered=true.

Test plan

• npm run lint passes
• npm run build passes

[Yurii214]

This updates both the webhook install/remove path and the shared repo-name normalization path so casing stays consistent across registration and uninstall flows.
Lint/build are passing locally; happy to adjust if you’d prefer a narrower fix.

[Yurii214]

This fix normalizes repo names across both admin and webhook paths, and also makes uninstall cleanup case-insensitive so legacy mixed-case rows are cleared correctly.
Happy to narrow or adjust the approach if you’d prefer a smaller patch.

[anderdc]

The case-insensitive removal (LOWER(repo_full_name) = :repoFullName) and the zero-row warning are good — keep both.

Blocker: normalizeRepoFullName() lowercases what gets stored in the repos table (installation.handler.ts added path). But the repos table is the canonical-case source of truth (see the comment at pulls.service.ts:50-51), and three sites match it exact-case against GitHub's canonical casing: webhook.service.ts:85 (findOneBy({ repoFullName }) — the registration gate), miners.service.ts:183/232 (LEFT JOIN repos r ON r.repo_full_name = p.repo_full_name), and pulls.service.ts:50. The PR/issue/comment/review handlers all still store raw canonical casing, so lowercasing only the repos row means any mixed-case repo would fail the webhook.service.ts:85 lookup and have all its events skipped as 'not registered' — the same silent-failure this PR is trying to fix.

Drop the stored-value lowercasing (the normalizeRepoFullName on insert, and don't have validateRepoFullName mutate casing for stored/keyed values). The case-insensitive removal alone fixes #120. Normalizing stored casing would have to be applied consistently across every write path and every exact-match consumer — a much larger change than #120 needs.

[Yurii214]

Updated. I removed stored-value lowercasing so repo rows keep canonical GitHub casing. The fix now only applies case-insensitive matching on removal and keeps the zero-row warning.