v0.5.0

Minor release.

Features:
- Fuzzy search: basename-centric fused re-ranking for better relevance.
- Trending searches leaderboard.

Packaging:
- .deb now published to the GitHub Release alongside rpm and pacman
  (release.yml now stages and uploads the Debian package).

No breaking changes; --public-base-url and all v0.4.x behavior preserved.