Add artifactapi remotes for jellyfin-ha auth plugins

jellyfin-ha bakes the LDAP and SSO auth plugins into its image, and all
outside artifacts must be fetched via artifactapi rather than direct.

- Add remote_generic/jellyfin.yaml proxying repo.jellyfin.org, scoped to
  the ldap-authentication plugin zip.
- Add a github.yaml pattern for 9p4/jellyfin-plugin-sso release zips
  (GitHub redirects release downloads to objects.githubusercontent.com,
  which the existing github remote already follows).

config/remote_generic/github.yaml

@@ -10,6 +10,7 @@ mutable_patterns:
   - "iplocate/ip-address-databases/raw/.*/ip-to-country/.*"
 patterns:
   - ".*/archive/refs/tags/.*.tar.gz$"
+  - "9p4/jellyfin-plugin-sso/.*/sso-authentication_.*.zip$"
   - "ahmetb/kubectx/.*/kubectx_.*_linux_x86_64.tar.gz$"
   - "ahmetb/kubectx/.*/kubens_.*_linux_x86_64.tar.gz$"
   - "apple/foundationdb/.*/libfdb_c.x86_64.so$"

config/remote_generic/jellyfin.yaml

@@ -0,0 +1,6 @@
+base_url: https://repo.jellyfin.org
+description: Jellyfin official plugin repository
+immutable_ttl: 0
+mutable_ttl: 7200
+patterns:
+  - "files/plugin/ldap-authentication/ldap-authentication_.*.zip$"