fix: expose custom packages as flake outputs for CI caching

Add packages output with:
- custom-* packages from packages/
- qt-pinned-jellyfin-media-player

Update CI to use hyphenated names (flake attrs can't have dots)

.gitea/workflows/ci.yml

@@ -27,12 +27,12 @@ jobs:
       fail-fast: false
       matrix:
         package:
-          - custom.claude-code
-          - custom.app-launcher-server
-          - custom.mcrcon-rbw
-          - custom.tea-rbw
-          - custom.rclone-torbox-setup
-          - qt-pinned.jellyfin-media-player
+          - custom-claude-code
+          - custom-app-launcher-server
+          - custom-mcrcon-rbw
+          - custom-tea-rbw
+          - custom-rclone-torbox-setup
+          - qt-pinned-jellyfin-media-player
     steps:
       - uses: actions/checkout@v6