fix: APK and APT services share ReleaseTracker causing skipped assets

[jdrouet]

Part of #59 — Discovered during #65

Problem

Both AptRepositoryService and ApkRepositoryService use the same ReleaseTracker backed by the shared github_releases table. When the APT service marks a GitHub release as scanned, the APK service will skip it entirely — even though the .apk assets in that release were never processed (and vice versa).

This means whichever service syncs first will cause the other to silently miss packages from that release.

Possible solutions

Option A: Separate tracking tables (minimal fix)

Add a dedicated apk_github_releases table so APK and APT track scanned releases independently. Low risk, minimal code change.

Option B: Unified sync pass (cleaner design)

Merge the two sync loops into a single RepositoryService that processes both .deb and .apk assets from each release in one pass. This avoids redundant GitHub API calls and ensures both package types are always in sync. Larger change — touches the APT service, worker, and config wiring.

Context

The github_releases table tracks releases by (id, repo_owner, repo_name) with no format discriminator. Both services call filter_scanned_releases() and mark_releases_scanned() on the same ReleaseTracker trait backed by SqliteStorage.