feat: add perles to CI binary cache

Extract shared package definition, add to flake packages output
and CI workflow so perles gets built and cached by Harmonia.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

.gitea/workflows/ci.yml

@@ -50,6 +50,7 @@ jobs:
             custom-rclone-torbox-setup
             custom-beads
             custom-gastown
+            custom-perles
             qt-pinned-jellyfin-media-player
             qt-pinned-stremio
             nix-deck-kernel